I'm not desperate.
There is one here on ebay for £342.99 GBP.
http://www.ebay.co.uk/itm/Apple-iPhone-5-Latest-Model-16-GB-Black-Slate-Unlocked-Smartphone-/400532061603?pt=UK_Mobile_Phones&hash=item5d41923da3
Or a simple sale here for £205 GBP
http://www.mazumamobile.com/sell-my-mobile/apple/mobiles/iphone-5-16gb/1959
As a guide I'd be looking for something between these two prices.
UK preferred as simple postage (special delivery).