I'm not sure what the pound is worth versus the dollar, so I can't help on the price, but I have a MacBook Pro 15" I got a couple of months ago, and I love it. It's an Apri 2010 model.
One thing I will say on price, by the way, is that a fair price is one that reflects the value it has to you, if within reason.
Assuming you have access to the machine to check it, look for dents, scratches, etc. in the casing. Check the drive's SMART status, and look at the number of cycles on the battery. Carefully inspect the screen for dead pixels or stuck pixels. Is the keyboard smooth and tight? Does the SuperDrive work? Check with Apple to see that the Serial number is legitimate and registered. Make sure the WiFi works properly. Check to make sure the speakers work well. If you have bluetooth devices, check them as well.
And if you buy it, enjoy! They're fine machines.