As
@Pauly has said, they wouldn't have gone anywhere near the cambelt tensioner on a 3rd service, so that bears no relevance - Still worth a mention of course
. There is a goodwill procedure with VW and the fact it must only just be out of warranty with full VW history, I think you will covered for the whole issue. However if you can contribute just the tiniest bit then you will get a 2 year warranty on the work and parts.