Is it a Twin turbo or N/A? Manual or Auto? Manuals fetch a little bit more.
Depending on condition, I'd say up to £1500 for the N/A Manual and about £2500 for the TT Manual. A little less for Auto's.
I've had 2 TT's one modded and it did a 12 second 1/4! Not bad for an automatic!
I couldn't cope with the 5mpg though!!!