Some dealers are just crap when it comes to warranty claims, some warranty staff clearly don't know what VW UK will reimburse on.
If VW UK say no for an item that another dealer would get the green light for the work, it would seem to me that the first dealer didn't explain it well to VW UK when submitting the claim or the dealer lied and didn't actually ask VW. As always, if you get the brush off from one dealership group then try another.