As long as you did NOT select the option identifying as the driver and that is the sum total of your appeal, you will be OK. If you did identify as the driver, then you have wasted the easiest ever way to get this cancelled. As long as the driver is NOT identified, APCOA have no way to transfer liability from the
unknown (to them) driver to the
known Keeper.
This is the normal appeal that is guaranteed to get the PCN cancelled, whether at Heathrow or any other airport that uses barrier-less (ANPR) entrapment for extorting the drop-off/pick-up fee:
I am the registered keeper. APCOA cannot hold a registered keeper liable for any alleged contravention on land that is under statutory control. As a matter of fact and law, APCOA will be well aware that they cannot use the PoFA provisions because [name of airport] Airport is not 'relevant land'.
If [name of airport] Airport wanted to hold owners or keepers liable under Airport Bylaws, that would be within the landowner's gift and another matter entirely. However, not only is that not pleaded, it is also not legally possible because APCOA is not the Airport owner and your 'parking charge' is not and never attempts to be a penalty. It is created for APCOA’s own profit (as opposed to a bylaws penalty that goes to the public purse) and APCOA 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 NtK can only hold the driver liable. APCOA have no hope at POPLA, so you are urged to save us both a complete waste of time and cancel the PCN.
So, did you identify the driver by selecting anything other than "Keeper" or "Other"?
Whilst the above appeal is guaranteed to get the PCN cancelled, it does not mean that you have to pay a penny to APCOA, because they are benign. They NEVER litigate but it does mean that you have prolonged the process by many many months because, if the driver is identified, they do have the name of the liable party. That means after a POPLA appeal which is unlikely to be successful, the Keeper will start to receive a load of useless debt recovery letters.
Debt collectors are not a party to the contract allegedly breach by the driver and have no standing to sue or do anything except to try and intimidate the low-hanging fruit on the gullible tree into paying out of ignorance and fear. You can safely ignore all debt recovery letters and, as far as anyone's concerned, you can use them as free emergency loo paper or shred them and use them as hamster bedding.
As it is APCOA, the debt collectors will eventually hand the case back to APCOA and they will give up and move on to more gullible victims. So, even if you do nothing else, nothing will come of this in the long run.
So, has the driver been identified?