I have. This one is only about 5 minutes walk from my house. Found it yesterday down a side street. Unfortunately some local taggers have tagged over it and ruined it (dunno if you can ruin graffiti but whatever), Some experts reckon it was worth around £20,000! It's now been tagged over and stuff... oh well! It's the girl with a balloon saying 'No Future' on his website http://www.banksy.co.uk/outdoors/outuk/horizontal_1.htm
So anyone else seen a 'real banksy'?
P.s I might try to get a picture of the current state of it tomorrow if there isn't too much snow :)