Totally over the moon that they reversed the decision. They had made it so that both of the original registrations were void, and issued a new vin.
I was going to have to get the old vin obliterated, get a new one stamped on to the chassis, get a new vin plate fitted, then apply for a VSA inspection which could take a month to get sorted, and then register it with the DVLA when they'd issue a Q plate.