Nice choice
Things to be aware of are
Rear springs can be snapped, usually towards the bottom and quite awkward to notice
Check condition of all brake discs as fronts can be around £190 each mark (they are semi floating type)
Rears aren't so bad at around £38 each
Manual so no Mechatronics unit to worry about
Dual mass flywheel can sometimes be prone to failure also check it goes into all gears smoothly
Engines can have coil pack failures (you could always check any potential car with Audi to see if it's had the recall applied) otherwise they are around £32 each OEM
If you have a friend with Vag-com get them to go along with you, that way they can check out if there are any fault codes stored, also get them to check blocks 208 & 209 for cam chain stretch (anything above -8 is not good)
Other things are Dashpod, make sure it reads all ok with no lines missing on the DIS and all the needles work as they should, again these can be fixed from anywhere around £150-£200.
Good service history showing regular oil changes is vital, should be Audi & independents and tally with the mileage.
Check the last time the Haldex oil & filter were changed, regular oil changes will keep it in tip top order.
Not sure about the manual gearbox oil and its service intervals, if any, you could ask Audi about that to make sure.
The main thing though is that the cam chain is in good order, if it's not you'd be looking at anything between £1200-£1800 to get it sorted, it's a big job.
I have to say since buying ours I love it, such a fabulous car and surprisingly good on fuel I think.