I'm not an expert but from reading magazines Audi engines are pretty hardy, the main thing is to check that it has a good service history. With that sort of mileage it should've had two cambelt changes, if it's only had one I would insist that the cambelt is replaced again before buying it as it's due around that time.
If you test drive it try and go over a few bumps and listen out for noises from the shock absorbers and bushes. Also check (or get a friend to check) the condition of the radiator, if it's bad then you will see where some of the fins have started to disintegrate.
Lastly, give it some welly to check that the performance is ok. If you feel any power loss when accelerating hard, then it could be several things. Many modern cars have a Bosch MAF (air flow meter) and these commonly die after 50,000 miles upwards. Typically you get consistent power loss at high rpm's.
The coils can also go, these are only about £20 each in the UK, but there's no way of telling which one has died (there are four). A dodgy coil wil produce a brief 'flat spot' feeling, like a misfire when you put your foot down.
Not trying to put you off as they are well built cars, but these are some of the main things to look out for on any car which has done a few miles. The best thing to do is drive it, and just have a look around it. That will often tell you a lot about how well a car has been looked after
