I just rolled over 100k miles on a 59 plate FR TDI CR170, owned it since 2015.
Issues from past experience;
Sticky calipers, done both the fronts at different times now one of the rears has started to stick a bit.
Patches of surface rust on the underside everywhere.
Air-con compressor "clutch" issue, don't replace the compressor just do the "clutch".
F15 fuse under bonnet setting itself on fire causing random lights to not work.
Leaky plastic bonnet panel causing the sound deadening to sag and go mouldy.
Bolts rusting into rear suspension bushes so you can't get the tracking done without replacing the bolts and bushes.
Rear suspension bushes deteriorating but due to how rusty and solid the components have become there is no play so passes MOT, but doesn't handle great.
Engine under-tray sagging in the middle causing it to scrape on some speed bumps (lowered on Sportlines)
Random squeak from rear suspension i've not managed to isolate yet.
The basic radio on the FL being a huge ugly waste of space with no features, that once a year will light up and play music but not display anything on the screen.
MFD LED's slowly dying, lost 2 since owning, one top left one bottom left.
All doors locks eventfully sticking at some point, drill holes in lock casing and lube.
Dealer replacing 3 of my broken springs FR springs with standard non-FR springs (didn't notice till i fitted Sportlines).
Leather on the gear gator deteriorating.
Paint on lower part of steering wheel worn through in places.
Outer thigh bolsters foam on seat degrading/going soft from climbing in and out, both driver and passenger side, i'm not a huge guy and our lass is only 5'3'' 8.5 stone.
Might need a bluetooth OBD scanner to check for other issues;
Throttle position stopper wearing on the plastic inlet manifold, cheap fix that takes a bit of time and dismantling.
Wheel speed sensors failing.
Auxiliary water pump fail.