Hi,
Welcome to the forum. Good luck with your future Audi purchase!
I'm NOT a know it all, but i can help with a few things...
1) The car in question is 5 years old. The waterpump and timing belts should be changed. I would hope for a metal propeller.
2) Check the rear wiper works, as commonly water can seep from the pipe that feeds the rear window onto the motor and fries it!
3) Check for any clattering on start up and with air con off and on. If the car is a manual it could be the dual mass flywheel on its way out though somewhat unlikely as its very low mileage unless the previous owner labours the car around everywhere.
4) I hate low mileage diesels, as diesels are built and designed for hauling weight around and long motorway journies. I wont get into an argument over it now, but check the MOTS to check that the car hasn't been clocked back.
5) Take the car for a very good spirited run. Make sure once the engine is warm it stays at 90 degrees and redline the car in 1,2,3rd gear to check for sticky vanes on the turbo (limp mode if problem). The reason i suggest doing this is 55k on a nearly 6 year old car is approx 9k a year. That suggests to ME that its been used locally around town etc and the odd stint on the motorway perhaps. Diesels create soot and carbon deposits everywhere. Especially on turbos when they are not used! Also check suspension for wear as local driving can have a deprimental effect on shocks, especially if the car is from a city centre etc where road calming measures like humps are used.
6) Good luck! I cant think of any other problems, but with low mileage diesels perhaps EGR valve problems etc in the future, but that can always be cleaned in the name of preventative maintenance.
NB: If the car has two exhausts on the left hand side then its the 140. The 170 bhp models came with twin exit exhausts, one on the left and the other on the right.
