It's not PoFA compliant. Only the
unknown driver is liable. As long as you, the
known keeper does not reveal the identity of the (
unknown to PGL) driver, inadvertently or otherwise, they will not be able to do anything except try and con you into paying or giving up the identity of the
unknown driver.
As the NtK does not comply with the requirements of PoFA, they cannot transfer liability for the charge from the
unknown driver to you, the
known keeper.
As simple appeal along the lines of this should be enough but as you are dealing with money hungry ex-clampers, expect the appeal to fail but it should win at POPLA. Do not amend except to add your VRM and PCN number.
I have received your Parking Charge Notice (Ref: ________) for vehicle registration mark ____ ___, in which you allege that the driver has incurred a parking charge. I note from your correspondence that you are not seeking to hold me liable as the registered keeper, under Schedule 4 of the Protection of Freedoms Act 2012 (PoFA). You have chosen not to issue a Notice to Keeper (NtK) in accordance with PoFA, and it is now too late for you to do so.
There is no obligation for me to name the driver and I will not be doing so. I am therefore unable to help you further with this matter, and look forward to your confirmation that the charge has been cancelled. If you choose to decline this appeal, you must issue a POPLA code.