You are advised to show all dates and times on the NtK in order to determine compliance with PoFA. From what can be seen, the wording is PoFA compliant. So, admitting to having been the driver will make little difference unless the dates are not compliant.
How long was the vehicle shown to be stopped? Does the evidence from the attendant photos show the vehicle stopped for more than 5 minutes?
Have you tried Plan A which is a complaint or request from the business/landowner of the location to have their agent cancel the PCN?
Plan B has been rejected with a convoluted interpretation involving PoFA which is irrelevant. You are dealing with intellectually malnourished scammers so don’t expect anything reasonable from them.
Plan C would normally be an appeal to the IAS (IPC member) but they are an exercise in futility. By all means waste your time with an appeal to them and if they cancel it, go buy a lottery ticket.
Plan D is your best bet now. A truly independent arbiter, a judge, will decide whether you owe a debt to CPMUK.
Unfortunately, you need to have the fortitude to weather a barrage of useless but scary (to the uninitiated and low-hanging fruit on the gullible tree) letters from debt collectors. They are powerless to do anything except to scare you into capitulating and paying into their scam.
You have to wait and see if they ever send you an LoC and a claim. If they do, come back and you can get advice. They have 6 years to do so. If you move at any time in those 6 years, you must instruct the DPO of the PPC auto update your address and to “erase” your old one. These scammers often rely on their victims not responding to a claim and getting a CCJ by default.
Follow the advice you get here and there is no risk of getting a CCJ.