Both British Airways and Turkish Airlines fly direct between London and Istanbul, but perhaps a cheaper method is to catch a European carrier, which will involve a stop off en route. You can also try flying into Antalya, Izmir or Ankara.
Travellers coming from western Europe can arrive by land via Greece or Bulgaria, or by ferry from the Greek Isles. There are border crossings with all eastern neighbours including Georgia, Armenia, Iran, Iraq and Syria, though safety varies and you should definitely research this in more detail before you travel. Travelling via the Black Sea to Russia and Ukraine is notoriously difficult.
NB. Remember, when travelling to Turkey check your passport expiry date. Passports must have at least 60 days’ validity from the date of expiry of a traveller’s visa, visa exemption period or residency permit to be able to enter the country.
Turkey’s lack of reliable railway is more than made up for by the superb bus network. Vehicles are invariably ultra modern and comfortable, and often come with an attendant who’ll serve you tea and coffee. The most daunting thing can be choosing from the myriad bus companies, which will invariably start touting for your business as soon as you arrive at a station.
It’s probably best to avoid driving in Turkey. Turkish drivers can be a little bit erratic and unpredictable which makes driving hazardous if you’re not used to it. Besides, the bus services are so good you don’t really need a car.