Sitting on the tip of the East, with western Europe just a stone's throw across the water, Istanbul is a city that has been through many cultural and religious changes, but has a truly modern, 21st century feel. However, it is still one of the world's best cities for amazing history, buildings and romantic tales, and somehow the atmosphere remains romantic and almost mystical.
With a Mediterranean climate, the best months to visit are between May and October, and although it can get very hot in the Summer, the waters of the Black Sea and the Bosphorus keep it pleasant. Try a visit in spring, and get swept up in the celebrations on the 19th May, for the Commemoration of Atatürk, Youth and Sports Day. Or perhaps leave it until October and join in Ramadan or Eid, and finish off with the republic day on the 29th of October.
Turkey is on GMT+2 hours, and British nationals need a visa, but it's available online. Also, passports should be valid for at least 6 months from the date of entering Turkey. Check these vaccinations are up to date: Hepatitis A, Typhus, Tetanus and Diphtheria. There are some fabulous markets, like the Grand Bazaar and the Egyptian Bazaar, but goods are often overpriced, because haggling is a tradition, and usual, so get some practice in first perhaps. Food wise, Istanbul is a fast food paradise, with street vendors and wonderful eastern European and middle Eastern dishes. Snacks are available from 2 TRY, kebabs from 8 TRY. Fish is expensive, and beer costs from 6 TRY.
Metro M1 to Aksaray - cost ca. 4 TRY. HAVATA shuttle bus to Taksim Square, every 30 mins. There are no buses between from 1am to 4am; cost: around 11 TRY. Taxi to Taksim ca. 60 TRY. Good, cheap public transport network: bus, metro, minibus, ferry, metrobus, tram. Istanbulkart: rechargeable and valid for all public transport. Taxis are more expensive than public transport but cheaper than in the UK. Accommodation starts from 1 night in a Hostel/Guesthouse from 30 TRY. Wide choice of accommodation in the districts: Eminönü (Blue Mosque, Grand Bazaar) & Beyoğlu (Taksim Square, İstiklâl Caddesi). Finally, 'The Prince Islands' are worth visiting: car free only horse drawn carriages are allowed.