@The Junkman
Steve,
UK registration numbers are allocated nationally by the Driver & Vehicle Licencesing Agency to the vehicle, not the owner. (Personalised plates are allowed but have to be part of the number plate register.) No numbers are duplicated. Each year new vehicles are given as part of the number, a year designation; there are 2 per year, every 6 months. For instance, the reg no of my Peugeot is WF55 XYP. The 55 means it was first registered in the second half of 2005.
However, kit cars, rods and other 'specials' can apply for an old, out of use, number either from the vehicle on which the 'special' is based or another 'dead' vehicle.
All that said, the car pictured not only has plates of dubious legality due to size and font (these are specified in the regs), it doesn't have mudguards/fenders. Also technically illegal.
steve