But he is not selling a car that does not exist. He is selling the log book and number plates. Not selling the title, just the bit of paper that gives him the title. He says openly that the car is scrapped.
Also, if the purchaser liked the number BFJ780B , it would be quite legal for him to tell the DVLA that the car was scrapped and apply to have the registration number transfered to another car
The only thing that would be dodgy would be if the purcheser of the bit of paper tried to use that to get the car registered in his name. Even then so what? I can't see anything dodgy.
People have been know to sell number plates from scrapped railway locomotives.