You really need to be aware of the Consumer Rights Act 2015, if you are considering rejecting the car
If you have a finance agreement in place (most typically with VWFS), you have what is known as a tripartite agreement under the Consumer Credit Act. The three parties are the debtor (you), the supplier (the dealer) and the creditor (the finance company)
You need to raise the rejection process with VWFS in the first instance, as they are the legal owner of the car and for the purposes of the law, VWFS are considered as the "trader", even though the dealer will have a role with any repair attempts or subsequent replacements.
Know your rights, and who to complain to.