Re. the plate, it might just be a made-up plate that was used by McLaren. The front one got shipped out with the car, and the owner kept it on. A lot of people like to leave European or Japanese license plates on their imported cars. The rear one was left behind in England, apparently, and used on the Harrods car. If it is a valid registration, all they would have had to do is get a new front plate made up. Takes 10 minutes and 10 pounds.
I tend to believe the story of the car getting repainted quite quickly, so I would think this is the other chassis. It probably needs a complete overhaul of the engine and all rubber hoses and seals if it has been sitting for so long. What a sad waste. And what a story!