You have said that the driver was aware that there are restrictions but chose to ignore them. From GSV, over various dates, there is some ambiguity in the signage you could argue as some signs simply say "3 hours max" although I did see one with the restricted times on it. However, they all say "for use only whilst shopping in store".
The entrance sign is also ambiguous, as it only says "3 hours max".
I would recommend, for now, simply sending the generic appeal response with a minor tweak as follows:
Dear Sirs,
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 seeking to hold me liable as the registered keeper, under Schedule 4 of the Protection of Freedoms Act 2012 (PoFA).
You have failed to fully comply with all the requirements of PoFA, namely paragraph 9(2)(e)(i) in that you have not "invited" (nor any other synonym of the word) me, as the keeper, to pay the charge. You will be well aware that partial or even substantial compliance with all the requirements of PoFA is not enough to hold the keeper liable for the charge. Only full compliance is acceptable. As such, your Notice to Keeper (NtK) does not meet all the requirements of PoFA to be able to transfer liability for the charge from the driver to the keeper.
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.
Yours,