If you are holidaying or traveling to Turkey after April 2014, you will need to be aware that you will need to have an e-visa prior to traveling.
This is the information from the Turkish consulate:
Deadline for the application of Stamp Visa and Banderole visa for entering the Republic of Turkey at the border gates
23/12/2013 - Announcement
Visa Applicants, Turkish Consulate General kindly request the following
information to be circulated; The application of Stamp Visa and
Banderole visa for entering the Republic of Turkey at the border gates
will continue together (simultaneously) with the e-visa application
until 10th April 2014. After the aforementioned date (10 April 2014) the
application of Stamp Visa and Banderole visa will be abolished and will
completely be replaced by the e-visa application. The citizens of the
countries who are eligible to get the banderole visa given at the border
gates will be able to enter the Republic of Turkey with getting an
“e-visa” online from the website "https://www.evisa.gov.tr" instead.
Turkish Consulate General would like to inform and emphasize the
deadline (10 April 2014) for the application of Stamp Visa and Banderole
visa for entering the Republic of Turkey at the border gates.
According to the general visa (for touristic purposes) rules, British
passport holders have the right to stay 90 days in 180 days. The day
you enter Turkey (not the day you get visa) is the first day of the
period of 180 days which means your right to stay 90 days duly starts
on the day you enter Turkey.
HERE IS THE LINK TO THE TURKISH CONSULATE LONDON WEBSIITE
THIS IS WHERE YOU CAN GET THE E-VISA