Update in case it is useful for someone else: mobile dent removal guy came and examined. The dent in the rear door is easily fixable without a paint job, but can't be accessed by the usual means and the door has to be dis-assembled to do it, advised a marque specialist needed so it's booked in with Vic at Migliore next week (approx 1-2 hours job). Dent man says it is the first time he has turned down a job in 15 years, and he does lots of Ferraris etc. Reasons are (1) the window is double glazed, leaving insufficient room for access via the seal, maybe could try but risky; (2) the wide shoulder of the QP - and the dent is of course on the widest part - means the usual tools aren't long enough to reach without then levering against the window (rear in a QP only goes down about 3/4 of the way) - double glazed are prone to breakage if pressed on the edge he says. He looked into accessing via the wiring loom into the door but couldn't do that either. He said someone else might be prepared to risk it, but I wasn't.
I'm already careful about where I park - thought I was safe enough in Brooklands members car park but obviously not! Feel like adopting the two spaces strategy from now on...