I think its all depends on the Engine - Do you know if the guy is looking to sell??
If he has the New Compomtive alloys which aint cheap, then my guesses the engine has been looked after aswel.

Could be worth upto £15k in my eyes depending on the condition.

Can i ask why you only want this car?? As for £13k you can get a nice one and maybe 1 with less miles