Is there any thing in what the garage says about the 2.5tdi being an unreliable engine?
I’ve had my 2.5 tdi for 5 years and have had two cambelt failures, 1st was knackered water pump but salvageable engine (i.e. no cracked pistons). 2nd time round after 60k spontaneous cambelt failure despite using genuine parts, reputable garage, new water pump tensioner’s etc. not so lucky new engine time. By the time i’d sold ancillaries, head, block etc. wasn’t too much of a hit but still frustrating i’ll be getting cambelt done every 30 – 40k as this is the achilles heel of the 2.5 tdi engine.
Sounds like you may have a good case against the garage but if they’ve cut corners they’re probably a slippery bunch!