You might be better doing a 'trial' run, perhaps taking in some of the winter months. It's different living in Turkey from being on holiday.
Once you take the BIG plunge you could think differently. As was previously stated 600 - 700 ytl a month is realistic. You have to think differently when it comes to shopping as all the things you like in the UK are expensive in Turkey, IF you can get them. Socialising is the way of living and when you're in your own place, you might want internet access which all adds to your monthly costs. Good luck.