@seanjean123 please stop trying to overthink this. No one guarantees anything but if you come here seeking advice from experts in these matters, then either follow that advice or simply pay the charge at the mugs discount rate!
All you need to know is that APCOA have no idea who the driver is unless you blab it to them, inadvertently or otherwise. The
known Keeper is under no legal obligation to identify the
unknown driver. Only the
unknown driver is liable. They cannot transfer liability from the
unknown driver to the
known Keeper because airport land is not relevant as far as PoFA 2012 is concerned.
Add to that fact, APCOA DO NOT litigate. If you did nothing, apart from a wave of useless debt recovery threats, nothing else would happen. Useless debt collectors are powerless except to try and persuade the low-hanging fruit on the gullible tree to pay up out of ignorance and fear.
So, send the appeal, EXACTLY as advised and that will lead to a cancellation. No guarantee but even if it didn't, nothing will ever come of this if you follow the advice. Or else, just pay it and we can spend our time more constructively advising others.