Did you receive confirmation from Park & Control that your current address for service has been updated? Did you send the Data Rectification Notice to the Data Protection Officer email address as noted in their privacy policy on their website?
You can safely ignore DRP+ and and any other useless debt collector. They are powerless to do anything and you can let them continue to waste their postage sending their rubbish to an old address. They are not a party to the contract allegedly breached by the driver. Never, ever, ever communicate with these useless debt collectors. Their only power is to persuade the low-hanging fruit on the gullible tree to pay up out of ignorance and fear. Ignore them.
If you never received the original Notice to Keeper (NtK) then you should send Park & Control a formal complaint which they are required to also consider as an appeal. However, you will require them to send you a copy of the original NtK and evidence of the date it was sent (actually entered into the postal system, not just generated.)
So, did you receive confirmation from the operator that the have updated your address? Do the signs at the location of the alleged parking contravention require blue badge holders to pay for their parking? Whilst a blue badge allows parking on public roads, they do not apply to parking on private land and the vast majority of unregulated private parking companies only require the bus badge to show eligibility to use the disabled parking bays, not that parking in them is free.
