Update: The recent visa changes that were announced by Turkey have been rescinded, at least for the time being, following representations from the British Ambassador to Turkey.

A visitor's visa valid for 90 days is issued to British Citizens at the port of entry on payment of £10 (English notes only) . British diplomatic/official passport holders must apply for a visa before travelling to Turkey.

Under new Turkish Immigration Procedures, effective from 14 July 2010, British nationals (and the nationals of 62 other countries) will still be issued with a 90 day visitor's visa on arrival. However, this visa can no longer be renewed after 90 days. The visa can only be used for a stay of up to 90 days within a 180 day period. You will now need to wait until the 181st day before you can apply for another 90 day visitor's visa.

If you wish to stay in Turkey for more than 90 days within a 180 day period, you will need to make a visa application to a Turkish Embassy or Consulate abroad or you will need to apply for a resident's permit to remain in Turkey. Please note that as yet this information has only been given to the British Embassy orally.
Staying in Turkey beyond the date of your visa is taken seriously by the Turkish Authorities

If you overstay you will be fined upon departure. Fines vary according to the length of time you overstay. If you overstay and are fined, you must apply for your next visa at a Turkish Embassy or Consulate overseas before you travel. You may also be banned from re-entering Turkey for a period of time as follows:-

Overstay 1-15 days - no ban.
Overstay from 16-90 days - banned for up to three months.
Overstay for more than 90 days i.e. from the 91st day, banned for up to six months.

This, if applied rigorously, may cause difficulties for resident British citizens who have not obtained an appropriate visa and or residence permit to reside in Turkey or simply for unwitting innocents who overstay their welcome.

For more information on applying for your new residence Visa please click here.