You probably already bought the car by now (or not)....but as with any car, look for signs of previous crash damage repair. Gaps between all doors and bonnet line up and are the same width, newly painted bumpers or bonnet etc.
Drives straight, and make sure that turbo pulls when it should. Listen for rattles in the motor....a little metal sound is sursprisingly normal on modern VAG engines, but obviously you dont want a noise that increases with revs, or when the engine gets warm. Timing chain tensioner can be an issue on these cars so a good service history is advisable.
If something looks, sounds and drives just fine, it usually is just fine. Just be thorough.