Here's the update - Left it there with VW since I actually had the same branch do my last service and was told it would only be €50 to have it kept in, tension adjusted and scanned over.
After a whole day I call back and they hadn't even looked at it. I get a call 20mins later and I'm told there's nothing wrong (clearly not, In physically watched the belt slipping). Now I'm told because I'm a previous customer they'll knock 50% off and it's only €102.
I'm now paying €102 even though they never actually did anything!!