For a belt and braces approach, you may wish to add something along the lines of the below onto the end of the appeals:
Even if the car park were relevant land, which is denied, your notice does not comply with the requirements of Paragragh 9 of Schedule 4 of the Protection of Freedoms Act 2012 in order to recover the charge from me as the keeper. For the reasons outlined above, I have no liability for this charge and look forward to your confirmation that no further action will be taken against me. If you choose not to accept this appeal you must issue a POPLA code.
