Well, I mangaed to do the cambelt yesterday - actually on my girlfriends golf turbo but AGU and identical to A3 1.8T so relevant here.
All went OK but a very time consuming job (thanks to HTC for his printout as helped no end - see his previous post)
Car has done 86k and to be honest belt, pulleys etc looked fine HOWEVER water pump showed signs of pink solidified coolant so I decided to remove it. Once off, the plastic impeller was breaking up and bearing was tight! glad I had a new one.
To be honest, I cannot see problem with belt surviving to 120k but something like a seized pump will be the reason for a snapped belt before this mileage (common problem on Audi V6s)
This whole job is DIYable if you have certain aptitude however a good range of tools are essential due to access and special fixings.
Would take about 4hrs+
Having now done the job, I would be very dubious about an independant garage quoting £165 etc to do the job as cannot see how they can do it propely for that price. There is also a lot to damage in the way of pipes, clips, connectors etc if you are careless.
Audi would be way to go if you cannot do yourself or a VERY trusted specialist.
Can expand further if anyone interested (in a hurry at moment!)