If your car has a fault, dealer has one chance to rectify it, not multiple goes. So unless this is a new different fault you can reject now because you notified them and they failed to remedy it.
When you say your contract is with VWFS, I presume you mean a lease (PCH where H is hire) or rental. They are the owners of the car, if it is faulty you deal with them for refund/replacement etc.
If you have a PCP (second P is purchase) then your contract is with supplying dealer. No one else. The finance companys only interest is loan being repaid (nothing related to maintaining or fixing the car).
You have no relationship with Skoda UK, they won’t process any refund so don’t waste your time asking them. The dealers have their own commercial contract with Skoda UK, but it has no legal link to your contract with dealer (so an excuse like we are talking to Skoda UK is just a delaying excuse), how the dealer subsequently claims from Skoda UK is irrelevant to you and your refund shouldn’t be delayed. If dealer doesn’t like way Skoda UK is behaving, not your problem, they need to use clauses in their commercial contract.