If you are in Istanbul then the British Consulate in Istanbul will be able to assist you with advice on marriage registration, applying for a passport or renewing a passport. They can also offer you advice on business in Turkey as well as provide you with consular assistance if you have been involved in an accident. They can also assist you with emergency travel documents if you have lost your passport while on holiday in Turkey.
The contact details for the Consulate has been listed below and you can contact them by telephone or in person on the street address provided. You can also email the British Embassy in Ankara for more information if the Consulate cannot assist you. If you are a BNO holder then you can also contact the Embassy about renewing your BNO while in Turkey. Each year thousands of British nationals flock to Turkey on holiday. Problems do occur so view the British Abroad leaflet for more information about Turkey and what you might encounter.
British Consulate-General Istanbul
Meşrutiyet Caddesi No 34