So they say you can't appeal by email, then take up much of the email responding to your appeal - having their cake and eating it? 
You could leave it, having made your point. Or you could respond briefly as follows:
Dear Sirs,
I note the contents of your recent correspondence. I welcome your confirmation that you have chosen not to make use of POFA legislation and are therefore not seeking to hold me liable for this charge as the hirer of the vehicle.
As I now have written confirmation from you that you are unable to recover the charge from me, I see no need to appeal further, as we seem to be in agreement that I do not owe you anything as the hirer of the vehicle.
I trust this will be the end of the matter, however, any further attempts to hold me liable will be vigorously defended.
Yours faithfully,
Response-
'Thank you for contacting Gemini Parking Solutions
My apologies for the delay in responding to you.
As previously advised, please head to our website and submit an appeal, if no appeal or payment is made within the stipulated 28 days then this parking charge will be passed over to debt recovery
Kind Regards,
Gemini Parking Solutions'
