What would be the reason for VWUK not to perform a visual inspection ? It certainly is cheaper to pay for a 5min visual inspection every 2 years than unnecessarily swap a cambelt every four years at 700 pounds a pop.
Your 8 year old biturbo might as well be fine, but that doesn't mean no other t5 BiTu ever had a prolem.
It is unquestionable and backed by many examples, also on this forum, that there were plenty of biturbos prematurely failing. At least in Germany, independent mechanics that diagnosed the failing engines found the oil was "cooked" due to high temperatures failing to lubricate the cylinder/pistons adequately. In the latest versions of this engines , (I think the EA288) an oil radiator, or bigger oil radiator was added to prevent the oil from deteriorating causing piston rings to be damaged , the oil then passing through, leading to even higher temp while the oil was being consumed, burned and deposited in the exhaust manifold with metal residues where it was actually found. .
It is not a theory, you can imagine in Germany there are also a lot of t5/t6 biturbos, probably a lot more than in the UK and the germans had the same problems with these engines. Not every single engine, but many enough, as people were asked to pay 15-17k € to replace their engine before reaching 100k km....