If you're driving an older car, you may be interested in one of the recently announced scrappage schemes. Many manufacturers in the UK offer generous contributions thanks to these schemes. Savings vary, with some offering a couple of thousand pounds off and others up to £8,000.
The way in which scrappage schemes work in conjunction with carwow offers is very brand and model-dependent - ranging from full scrappage savings in addition to carwow savings through to none.
Ultimately it is at the dealer's discretion, so you should enquire with them directly to find out what they are willing to offer.
You can find out more about scrappage schemes here.