Ive just paid my VW pcp off(I had it for the £1000 deposit contribution)-when I phoned up after 5 days to give 14 days notice, she said now you have given us your notice you have got 30 days to pay it off without accruing any further interest,(they were charging me interest of £5 odd a day,so it added £27 pound odd onto the settlement) but she did stress once you have given notice there is no going back (not that that really mattered to me) to the deal.
So the moral is I suppose, give your 14 day notice as soon as poss after picking it up and you will pay less interest.
I have not received the confirmation of my payment yet so I hope its all gone through ok!