I went to the garage at lunchtime and rescued the stereo :-) but thanks for the reminder – I would have forgotten if my dad hadn't mentioned it on the phone last night.

I checked with Parkers just now, actually, and they reckon it's actually worth less than Direct Line are offering. (In favour is a good service history and low mileage; against are some old scrapes from stationary objects that I never bothered to get fixed...) So I've probably done all right there.