It's for a PCN from an unregulated private parking company, Park & Control, an affiliate of APCOA.
@taksin... stop trying to contact DRP. Never, ever, ever, ever, ever, and I stress... EVER, contact a debt collector. They are powerless to do anything and their job is to scare the low-hanging fruit on the gullible tree into capitulating and paying up with scary words like "bailiff" and "CCJ". They cannot do anything and can be safely ignored. I repeat... ignore DRP and DO NOT communicate with them.
The first thing you must to is check that the address on your V5C is your current address. In the vast majority of case where no initial Notice to Keeper (NtK) is received but a debt collector finds your address is because when you last moved, you may have update your drivers licence but did you also update your V5C? Updating one, does not update the other.
P&C are IPC members so you're not going to get much help by complaining about not having received the initial PCN or reminders. You are past any appeal stage and now in a sort of limbo.
For the time being, ignore any and all debt collector letters. If/when you ever receive a Letter of Claim (LoC) which may seem like a debt collector letter but it will actually give you 30 days to pay rather than the usual 14 days, then come back and let up know and we will advise on the next steps.
If P&C are anything like their affiliate company, APCOA, they will not litigate. However, if they do, that is a good thing and you can easily defend any claim. There is no danger of getting a CCJ if you follow the advice.
Oh, and stop offering to pay the original "fine". It is not and never was a "fine" I will personally give you £100 for every occurrence of the word "fine" you can find on any of the correspondence you received. It is simply an invoice for an alleged breach of contract with P&C by the driver. Nothing more and nothing less. Do you pay every invoice you get without knowing what it is for and whether you even owe the alleged debt?
DO NOT offer to pay the original amount. Whilst it is not likely this will go all the way to a court claim, even if it did, it is easy to defend and in the vast majority of cases, they will discontinue once they realise that you are not so gullible after all and they go off in search of lower-hanging fruit to pluck.
If your V5C address is not correct, get it sorted ASPA. Easy to do online. If the address was an old one, you MUST send a data rectification notice to the DPO of P&C instructing them to update their recored with your current address for service and to erase your old address and to notify you when they have done so. Also instruct them to do the same with any third party they have distributed your DVLA data to.
The highlighted words are there for a reason and you must use them in your data rectification notice. Leaving P&C with a choice of two addresses is a sure fire way of getting a CCJ by default which is a PITA to untangle.
So, no contacting DRP or any other debt collector and do nothing else, except rectify your data with P&C, until or unless you receive an LoC or an actual claim form. Then come back for advice.