Tell them they have made an ANPR mistake and if they pursue this any further you will account for all your time and costs in defending their fraudulent accusation and will sue for the return of these costs using the small claims track of the county court.

Also write to the DVLA demanding an explanation as to why it released your date protected details illegally to these people because they cannot have shown 'just cause' for obtaining them. Law here: www.honestjohn.co.uk/faq/private-parking-penalties/