Just adding to this as a customer that's just withdrawn from a PCP agreement, having signed up during the Skoda Plus Event (£750 dealer contribution plus two years' MOT, Servicing, Recovery and Warranty).
Picked up the car on a Saturday, phoned VWFS asking to withdraw on the Monday which froze the balance with just under £10 extra on top of the list price. Everything confirmed on the phone but waited for the 'Right to Withdraw' letter to arrive before paying off the balance (you get 30 days to do so from the moment you ask). Now just waiting for the clearance letter to come through saying the car is ours which should arrive within 10 days.
We didn't have to make up the balance for the dealer contribution and we've kept the servicing plan as it's not connected to the finance agreement.
Hopefully helpful for someone else that ends up searching and reading various threads as I did before purchasing!