I keep seeing people referring to the other set of plates in the car, they aren't legal plates & can't be used on the road so they are irrelevant, to me it just supports the fact they were going to be used in the last car football part which is obviously going to be off road. Why would they have the plates for that section of the show if they never intended to get there?
Co-Incidences happen, I bought a Ford Capri in 2005 when I worked for the Department for Work and Pensions, it took over 6 months for anyone to spot the connection (A122DWP) despite the fact it was probably the oldest, loudest & most unusual car in the car park.
The classic car dealer they bought the car from has also said he was contacted by the BBC specifically looking for a Manual 928 which are rare (currently only two on Autotrader, both of which are expensive) and it was purchased a month before filming started, if they planned the show around the car then they are incredibly well organised.