Can't you have a word with your dealer Bear and get them to tell you whether or not your part ex value will be honoured? After all, its their (VW) fault that you haven't got your car yet so why should you lose out?
I could but I don't have much faith in my dealer. They seem to say only one of two things when I talk to them:
1. "We know nothing, we'll call you when we do" and they never call. Didn't even do so when I finally went BW confirmed until literally 5mins after I sent an email to VW exec demanding an update!
2. "As far as we know there are no issues, you can still expect July/August delivery"
Maybe I could convince them to take my car and give me a courtesy car, but I don't want that really as explained above. Also it seems that they have to claim compensation from VWUK and I have no faith in their ability to do this so I'd just be waiting indefinitely on them agreeing something with VWUK. The answer will probably arrive in a month: "computer says no". So I'd rather just go to VWUK myself and badger them for compensation myself rather than them compensating the dealer.