How much could I get for a brand new Iphone 4S 16GB unlocked?

I might be getting one as a part exchange with a item I'm selling and want to know how much I would likely get for it (GBP only please). I'm guessing it's something like 350

It is going to be high because it is unlocked. It will most likely cost about 430. Because you are having to pay full price plus some more because you can go to any company you want to. They make it crazy high so you will just get one with one of the big named companies. You can get on locked cheaper but you would have to pay someone to unlock it but you will save like $100 or so.