1. Ile de Porquerolles, France
Just off the Côte d'Azur, in the gulf of Hyères, this island is small (7km by 3km) but special, complete with superb beaches, great snorkelling, pine forests and vineyards. Most of it is a national park and there's a strict limit on visitors, although you can reserve your place in advance by booking in at one of the hotels.
Getting there: Ryanair (ryanair.com) flies to Toulon-Hyères from Stansted, followed by 10-minute bus ride to La Tour Fondue, and half-hour ferry to the island (return fare from €16.50, timetables at tlv-tvm.com)
Where to stay: Le Mas du Langoustier (00 33 494 583009; langoustier.com) is a four-star hotel with a gastronomic restaurant, close to the beach (doubles from €179)
2. Sylt, Germany
With sovereignty passing between Denmark and Germany like a beach volleyball, Sylt is an improbable but utterly endearing blend of wholesomeness and deep, Michelin-ingrained luxury. The strandkorbe - wicker chairs that perch on the sand - are a joy, the beach saunas (after which you race into the North Sea in various states of undress) particularly Teutonic. Linked to the mainland by a train track (on to which many a Mercedes and BMW will be loaded in the course of a summer) this is the sort of island where you bicycle to a tea shop housed in a thatched cottage and then head to a beach bar for some stylish clubbing - we recommend Sansibar.
Getting there: Air Berlin (airberlin.com) flights from Stansted via Düsseldorf to Sylt cost from around £192 return
Where to stay: Hotel Reethuus (00 49 465 198550; reethues-sylt.de) is thatched and serene; doubles from €120 B&B
3. Kvarken archipelago, Finland
The Kvarken is a collection of 7,000 islets stretching across 150km that Finns delight in canoeing between. The land is rising, by 8mm each year, meaning the shapes and sizes of islands are constantly changing. Scientists estimate that it'll be one solid (if slightly soggy) landmass in 2,500 years. Don't expect glamour, do expect to bond with your midge spray, but the scenery is stunning, the sense of peace tangible.
Getting there: Finnair (finnair.com) from Heathrow or Manchester via Helsinki to Vaasa where bridges link the two main islands, Replot and Bjorko
Where to stay: Bjorko Cottages (00 358 505 262300; bjorkocamping.com) has two log cabins by the sea on the island of Bjorko, plus the obligatory sauna, from €80 a night, €420 a week
4. Porto Santo, Madeira
More than just a satellite of its famous neighbour, this island, just 12km by 7km, is now beginning to make its mark on the tourist map with smart spas, golf courses and more than 50 restaurants. Vila Baleira is the sleepy capital, all whitewashed houses, shady squares and a perpetual air of siesta. Above all, people come here for the beaches; the golden sand is said to have healing properties. Manchester United striker Ronaldo, born in Madeira, is said to be planning to build his own hotel here.
Getting there: Easyjet (easyjet.com) to Funchal, followed by either a 20-minute flight (sata.pt, from €105) to Porto Santo, or a two-hour ferry (portosantoline.pt, from €51)
Where to stay: The Hotel Porto Santo (00 351 291 98 0140; hotelportosanto.com) is simple but is set on the beach. Holiday Options (0844 477 0452; holidayoptions.co.uk) offers a week's package with flights (international and internal) and breakfast from £1,015pp
5. Skomer Island, Wales
Just off the coast of Pembrokeshire, this is a perfect Enid Blyton-style island (minus reprobate grown-ups). Measuring three square miles but packed with wildlife, including 6,000 pairs of puffins and a large colony of seals. Book well ahead for accommodation in September when the seal pups start swimming.
Getting there: By ferry (£17 adults, £6 children, 25-minute journey) from Martin's Haven between April and October
Where to stay: A farmhouse provides self-catering accommodation (01239 621600; welshwildlife.org). Sleeping up to 15, from £35 per adult, £15 per child
6. Hamneskar, Sweden
Recently tipped for great things by Condé Nast Traveller. A 19th-century lighthouse is pretty much the only thing on this rocky outcrop on the west coast of Sweden, and now it presides over an acclaimed restaurant, while the buildings once inhabited by the light keepers are now a collection of hotel rooms. Walking around the island takes a grand total of 30 minutes.
Getting there: Scandinavian Airlines (flysas.co.uk) from Heathrow to Gothenburg, a bus to Marstrand (one hour), followed by a 10-minute speedboat ride
Where to stay: Paternoster (00 46 303 61845; kurspaternoster.se) charges from £154pp for accommodation, transport and evening meal
7. Amorgos, Greece
This place makes the average Greek island seem like Manhattan. Seriously quiet, seriously remote, although the new Blue Star Line ferries have made access faster. Above all, there's very little to do. This is a part of the Cyclades that has avoided such Grecian must-haves as museums or ancient ruins (although there are a couple of monasteries). Nightlife is centred on a handful of coffee shops in the extraordinarily calm town of Katapola. Shaped like a whale, take at least twice as many books as you think you'll get through.
Getting there: British Airways (ba.com) flies from Heathrow to Athens, taxi to Piraeus port for Blue Star ferry to Amorgos (around seven hours, timetables on bluestarferries.com)
Where to stay: Sunvil Holidays (020 8758 4758; sunvil.co.uk) offers eight nights' half board accommodation at the two-star Hotel Pagali £1,094pp (two sharing), including flights and ferry transfers.
8. Vega Islands, Norway
Lesser known than the Lofoten Islands, the Vega archipelago now has the Unesco seal of approval. Like much of Norway, it's an ornithologist's dream. Chief among the bird population are eider ducks, raised for their feathers - the houses built for them to nest in can still be seen, alongside lighthouses, fishing villages and dramatic Nordic landscapes.
Getting there: Fly to Trondheim with SAS (flysas.co.uk) from around £235 (via Oslo). Get a hire car and drive to Bronnoysund. Ferry to Vega Islands from £7 (around 50 minutes, timetables at 177nordland.com)
Where to stay: Vega Havhotel (havhotellene.no) overlooks the Atlantic, doubles from £120 including breakfast
9. Gigha, Scotland
The most southerly of the Hebrides and just seven miles long by half a mile wide, Gigha is blessed by unusually good weather for the area produced by its proximity to the North Atlantic Drift. The mild climate has helped create the world-famous Achamore Gardens, and the sunlit beaches offer idyllic walks with a good chance of spotting seals and otters.
Getting there: The nearest airport to Gigha is Glasgow, which is two and a half hours drive from Tayinloan, from where Caledonian MacBrayne (08000 665000; calmac.co.uk) runs ferries to Gigha taking 20 minutes (from £16 one-way for a car and two passengers)
Where to stay: The Gigha Hotel (01583 505254; gigha.org.uk) has double rooms from £48pp per night, B&B
10. Fanø, Denmark
Proof that Scandinavia has a knack with islands. Fanø, covering 56 square kilometres, is ringed by white sand beaches, laced with cycle paths and studded with villages, all with tasteful craft shops, cafes and bars. There's even a brewery, Bryghus Fanø. Very family-oriented and easy to get to from Britain, especially if you live in East Anglia.
Getting there: Ferry from Harwich to Esbjerg with DFDS (18 hours; dfdsseaways.co.uk) from £222 with car. Another 12-minute ferry from Esbjerg to Nordby on Fano (timetables on fanotrafikken.dk); a car with up to nine passengers costs from 370kn (£45)
Where to stay: Villa Qusisana (feriefanoe.dk) at Fanø Bad, right on the beach) from 500kn (£60) a night
11. Walney, England
Just half a mile from Barrow-in-Furness in Cumbria, and connected to the mainland by a bridge, this is perfect for nature lovers; just 11 miles long and a mile wide, it's home to 250 types of birds, 450 flowering plants and 400 species of moths and butterflies. There are two nature reserves; at South Walney Nature Reserve, the biggest gullery in Europe with lesser black-backed and herring gulls, visitors can witness a bird-watching spectacle so incredible that it has become known as "dive bomb alley".
Getting there: Drive over the Jubilee Bridge from Barrow-in-Furness.
Where to stay: The Brow Head Hotel (01229 473600; browheadhotel.co.uk), doubles from £65, including breakfast.
12. Procida, Italy
Thoroughly out-glitzed by neighbouring Capri and Ischia and all the nicer for it. It is just four sq km and the main harbour town of Marina Grande is everything you'd want from an Italian harbour port; coloured houses, washing lines and rocky inlets. An especially enticing part of the Gulf of Naples, Procida's film-set quality has been been immortalised in The Talented Mr Ripley and Il Postino. Another island, Vivara, linked to Procida by a walkway, is a nature reserve.
Getting there: Easyjet (easyjet.com) flies to Naples from Stansted and Gatwick, followed by a half-hour ferry (snav.it).
Where to stay: Hotel La Casa sul Mare (00 39 081 896 87 99; lacasasulmare.it), doubles from €90, including breakfast
13. Lopud, Croatia
Croatia has islands to suit every mood but Lopud is one for purists. Only two miles wide, with no cars, the Dubrovnik elite have used it as a hideaway for decades. For somewhere so idyllic, it is rather easy to get to - there are regular ferries, as well as speedboats from Dubrovnik. No roads - and unusually for Croatia, there are sandy beaches here, especially Sunj with its gently shelving white sand.
Getting there: British Airways (ba.com) flies from Heathrow to Dubrovnik. Jadrolinija ferries (jadrolinija.hr) take 50-60 minutes and costs around £4
Where to stay: La Villa is a homely, 16th-century seaside hotel on the island. Book through i-escape.com/lavilla.php - doubles range from €70-135 per night including breakfast
14. Ile d'Aix, France
Overshadowed by the all-Gallic glamour of nearby Ile de Ré, Ile d'Aix is an island with its own personality and character and is reached by ferry from La Rochelle. Tiny, but with an all-important bakery and several good restaurants. Napoleon spent his last week on French soil here; the house he stayed in is now a museum.
Getting there: Ryanair (ryanair.com) flies to La Rochelle, followed by ferry from the harbour, €13.20 return (20 minutes; timetables from service-maritime-iledaix.com)
Where to stay: Le Logis des Paillotes sur L'Ile D'Aix (00 33 6 14 37 08 03; leslogisdespaillotes.com) has chic but low-key rooms from around €78 a night.
15. La Graciosa, Canary Islands
Lying just north of Lanzarote, La Graciosa is part of the Chinijo Archipelago, and was declared a nature reserve in 1986. The island has a population of just 500 and is barely touched by tourism; long stretches of beach lie deserted, and the sandy streets mean there are few cars apart from the odd four-wheel drive. There is only one village, Caleta del Sabo, with a handful of fish restaurants and small shops. Life is simple, peaceful and utterly relaxed.
Getting there: Thomson (0871 213 4787; thomson.co.uk) flies from Gatwick and several regional UK airports to Lanzarote. Ferries from the port of Orzola take 20 minutes to reach La Graciosa (lineas-romero.com).
Where to stay: Cachet Travel (020 8847 8700; cachet-travel.co.uk) has a week at the Apartments el Sombrerito from £495pp per week, sleeping two, including flights and ferry crossings.
16. Sveti Klement, Croatia
The largest of the Pakleni Islands, which lie a short boat-taxi ride from the island of Hvar, Sveti Klement boasts sandy coves and pine-backed beaches and the picturesque hamlet of Palmizana where a clutch of elegant villas lie surrounded by pine forest. The Meneghello family have lived on Sveti Klement since the 19th century, creating a lushly beautiful botanic garden along with villas, bungalows and a renowned restaurant.
Getting there: Easyjet (easyjet.com) flies from Gatwick and Bristol to Split, then a two-hour ferry to Hvar (jadrolinija.com)
Where to stay: Book a cottage at the Menenghello (00 385 91 478 3111; palmizana.hr) from €80 per night and they can arrange a boat taxi from Hvar Town
17. Kastellorizo, Greece
The most far-flung of all the Greek islands, Kastellorizo is located east of Rhodes, close to the Turkish coast. There is only one settlement on the island, called Kastellorizo, or "Chora", which means "village", full of quiet alleyways, brightly coloured houses, neoclassical mansions and charming harbourside tavernas. The island has no beaches, although rocky grottos make it perfect for snorkelling.
Getting there: Thomson (flights.thomson.co.uk) flies from Gatwick, Manchester and Cardiff to Rhodes, from where it's a six-hour ferry transfer to Kastellorizo (timetables at gtp.gr)
Where to stay: The Margarita Hotel in Chora (00 30 273 6031711; hotel-margarita.com) has 12 traditionally-furnished rooms, which start from €60, including breakfast
The following correction was printed in the Observer's For the record column, Sunday June 28 2009
In the item above, we recommended the Margarita Hotel in Chora. In fact, this hotel is in a village with the same name on Kythira, not Kastellorizo.
18. Lismore, Scotland
Located in Argyll, Lismore's name comes from the gaelic word "lios-mor", meaning great garden - and the island's fertile soil means it lives up to the name, covered in wildflowers and home to more than 130 species of bird. Lismore offers simple pleasures; there is a good network of little-used footpaths and the relatively flat terrain means its great to explore by bike. Its location, surrounded by the waters of Loch Linnhe, means breathtaking views in every direction.
Getting there: Caledonian MacBrayne (08000 665000; calmac.co.uk) runs ferries from Oban to Achnacroish (around an hour; from £32 one-way for a car and two passengers).
Where to stay: The Old Schoolhouse (01631 760262; baligarve.co.uk) is a B&B with two comfortable rooms from £17pp per night, with dinner available.
19. Alicudi, Italy
The volcanic Aeolian Islands lie off the north coast of Sicily, remote and peaceful with dramatically beautiful landscapes enriched by the volcanic soil. Alicudi is the furthest west - and quite possibly one of the most isolated islands in the whole of the Med. Electricity and TV only arrived in the 1990s, there are no marked roads and just one hotel and one restaurant. What there is, however, is crystal-clear water and utter, blissful peace.
Getting there: British Airways (ba.com) fly to Catania from £160 return. It's an hour and a half by bus to Milazzo, from where ferries to Alicudi depart (around three hours; timetables at usticalines.it) .
Where to stay: The Hotel Ericusa (00 90 988 9902; alicudihotel.it) has doubles from €70 half-board.
20. Heybeliada, Turkey
Under an hour by ferry from Istanbul, Heybeliada is the second-largest of the Princes Islands that lie in the Sea of Marmara and far less crowded than its big sister, Buyukada. It is car-free, with horse-drawn carriage rides offering tours of the pine-clad hills and sleepy villages lined with tea-gardens. There are narrow beaches and the atmospheric 11th-century monastery of Ag Trias.
Getting there: British Airways (ba.com) flies from Heathrow to Istanbul; ferries from the Kabatas port run regularly, cost about £2 each way
Where to stay: The Merit Halki Palace (00 90 216 3510025; halkipalacehotel.com) is a former 19th-century school converted into a luxury hotel, with doubles from €100, B&B.