The banks in Turkey will accept your ATM card. My advice would be to take say �50 worth of YTL(New Turkish Lira) and then draw out you dosh from the hole in the wall as you would do at home. The bank will charge you �2.50 per transaction, so get say �100 out at a time. It is more convenient and safe than taking a lot of cash with you.
In holiday resorts they like � sterling and Euros. You will have no problem changing that to YTL.
Approx:
2.5 YTL = �1
so 10 YTL = �4 etc