Quite expensive isn't it? =[
[doublepost=1454176123][/doublepost]£999 for a used 17" 2011 macbook pro. Yikes.
Have you looked at refurbished Macs from Apple? A 2014 retina MacBook Pro is £1309.
Honestly I'd go that route. You'll get a computer with a full 1 year warranty and it'll supported longer.