I understand from other expats. that you need to get your residency first in order to buy a car in your own name. Cars are generally expensive in the Fethiye area, especially used cars. Expect to pay £3-£4,000 for a 5-6 year old tofas/fiat. New cars, if you can afford one, are similar to u.k. prices, but you will get a better deal generally from Antalya dealers, and if possible, take a turkish friend with you to help you secure a good price.
I understand that the u.k. driving licences are o.k, but it might be worth updating to the new european ones.
Good Luck with your move.
Pete and Jo