"The Sheriffs Are Coming" type programmes do HPI checks. If a vehicle is found to be on finance they can't take it "because it belongs to the finance company". Sometimes the Sheriffs repossess cars on the behalf of finance companies. I did hear of a case where a guy bought a car in good faith which was under finance and he was allowed to keep it. I can't remember any other details though.
But that is a different situation, they can not repossess property belonging to someone else, but when you buy a car in good faith, the seller is representing that they are the owner of the car and the law seeks to provide some protection to the innocent buyer hence the sale would need to for a valid disposition under HPA '64

. On the advice of my insurance company I had it valued (£6k) and they sent the report to the other company who responded that as it was now worth 6 times what they had paid out there obviously wasn't much of their vehicle left, but for £1k I could buy the original registration number off them
. My insurance company said they were trying it on and advised me to turn down their kind offer which I did. Never heard anything more, ran the RR for a few years and sold it without any problems 