You are only appealing as the Keeper. They are going to get your details as the Registered Keeper anyway if you don't appeal and then send you a Notice to Keeper (NtK).
So, if they will only accept the appeal by email,
then you use the following and save it as a PDF and attach it to the email. Just checked their site and you can simply copy and paste the appeal that has been provided below.
Do not identify the driver... as long as the
unknown drivers identity is not revealed. There is no legal obligation on the
known keeper (the recipient of the Notice to Keeper (NtK)) to reveal the identity of the
unknown driver and no inference or assumptions can be made.
The NtK is not compliant with all the requirements of PoFA which means that if the
unknown driver is not identified, they cannot transfer liability for the charge from the
unknown driver to the
known keeper.
Use the following as your appeal. No need to embellish or remove anything from it:
I am the keeper of the vehicle and I dispute your 'parking charge'. I deny any liability or contractual agreement and I will be making a complaint about your predatory conduct to your client landowner.
As your Notice to Driver (NtD) does not fully comply with ALL the requirements of PoFA 2012, you are unable to hold the keeper of the vehicle liable for the charge. Partial or even substantial compliance is not sufficient. There will be no admission as to who was driving and no inference or assumptions can be drawn. PCM has relied on contract law allegations of breach against the driver only.
The registered keeper cannot be presumed or inferred to have been the driver, nor pursued under some twisted interpretation of the law of agency. Your NtD can only hold the driver liable. PCM have no hope at POPLA, so you are urged to save us both a complete waste of time and cancel the PCN.