The currency is the Turkish Lira, the currency code is TRY. 1TRY consists of 100 kurus. The exchange rate is approximately 1GBP = +/- 3TRY. The banknotes are 5TRY, 10TRY, 20TRY, 50TRY, 100TRY and 200TRY; coins come in denominations of 5Kr, 10Kr, 25Kr, 50Kr, 1TRY, 2TRY.
All major credit cards are widely accepted for just about anything. Because of the charges from the banks majority of the Turkish shops have more than one card machine (5 - 6 is quite common) - if your card does not work with the first card machine, don't worry - they will try another one (you are not being ripped off!).
One of the easiest ways of getting hold of your money is to withdraw cash from ATMs using your credit or debit card (your bank may charge you for this). ATMs can be found all over the city.
Most banks are generally open Mon-Fri from 09.00 until 17.00.