The last few times we've been to Turkey, we've hired from Pandora Car Rentals who are based just outside of the airport. Their cars are fully insured with no excess and you can pay in cash on arrival. They have been highly reliable and last week when we decided to go at the last minute to Turkey for the Bank Holiday were able to supply a car with 8 hours notice to be collected at 4.00am! Great service. The cost was £20 per day.