Thats quite a nice example, silver ones seem to fetch less for some reason. I managed to get mine for only a few hundred more than that but 14k less miles.
I love my Cupra 20vt, i wouldnt change it for the world, and now i have pumped the tyres up to the correct pressures i can get 35 mpg quite happily. (for me thats fine - i would rather that and have the noise and atmosphere of a petrol turbo)
Each to their own at the end of the day, personally i reckon if you offer him 7.750 he should take it or negotitate at least.
What pressure are you running your tyres at? I can't find that perfect figure