Here is what a real 'Notice of Enforcement' looks like, together with DCBL's fake notice of enforcement. The differences are highlighted for your convenience.
This therefore appears to be a clear case of impersonation of authority scam.
The Prankster suggests anyone who gets one of these letters complains to Trading Standards, their MP, the BPA and the Parking Operator.
Here is some information on real Notices of Enforcement from Citizen's Advice.
The Parking Prankster