I have had my October 1995 300 tdi since March 2010 and here is what I have learned considering my vehicle is 15 years old and I abuse it off roading and greenlaning.
Inner wings are made from cheese and they don't last long.
Rear boot floor is also made from the same substance.
Always change the Cat exhaust pipe for a straight through de cat pipe as it generally has collapsed and just clogs the engine and makes it extremely under powered.
Off roading will cause an amazing amount of alternator issues.
As mentioned before, when having alternator problems, due to the lack of electrickery the car can be driven with a flat battery but remember no lights, indicators or radio....but it'll get you home.
Complete brake discs and pads renewed for £100....Winner!
Cheap parts, try compering parts for a TD5 with parts for a 300 tdi.
Hold their price, mine cost £950 and i won't lose money on it.
They do leak, every possible combination of leak, swivel pins, transfer box, gearbox, engine, axles, steering box, vac pump.
Bin the EGR valve and clean the intercooler.
I am sure there is so much more.