Do you have a property in the UK that you could rent out to give you a steady income?
You probably could just about manage on £500, just basic living costs, depending on how you want to spend your days,but if you're coming here to enjoy the area and all that it offers, make friends, go out socially,help with charity work, have a hobby, take Turkish lessons, travel etc you don't want to be worrying about every penny and not making the most of it.
I don't know if you're planning to have a car, but these are very expensive and expensive to keep on the road too.
Are you bringing your own furniture etc? Again, these things aren't cheap, even kitting out your kitchen with basic equipment is expensive, so you will need a budget for these things too, and wont be able to do all of that out of the £500 a month.
Also bear in mind that when family and friends come over you will want to go and show off your lovely new country and will find that you tend to live like a tourist while theyre here.
You also need to factor in travel back to the UK, for visits, or in case of any emergencies.