Can you post up the rear of the PCN one can see that the PCN is a reminder if you have the original post that one as well as any signage.
If there are multiple businesses then they cannot place terms and conditions without landowners permission. So for example if the driver parks on a part of the land to collect items and they have no contract with a parking company then they cannot issue a PCN.
This will possibly end up in court so you need as much evidence as you can gather. There is very little point in communicating with the parking company and do not communicate with any debt collectors. Only reply to a LBC should this arrive with an outline of your defence.

You can just stick with non compliance with POFA and send that. If they decline the appeal then you can look at the no return time at another time and include that as well. Do not under any circumstances name or indicate the driver details.

Just sit tight and see what happens then come back here for advice if required.

Can you post up signage in relation to where the car was parked ordinarily on public roads displaying a blue badge in these circumstances is acceptable but this is not the case in private parking scenarios. The creditor aspect is also ambiguous it shouid be quite clear but this would be open to interpretation.

I don’t think all is lost on the 14 day rule on POFA requirements as you seem to indicate we on a number of occasions. As long as you have been consistent in your appeal. Under certain circumstances there may be a little game of ping pong with IAS in my experience. So when or if they ask for further information regarding the grace period you can go in with POFA non compliant to bolster up the drivers defence. If you can start using the driver instead of we. Don’t get  hung up by any mention of Elliott Vs Loake if this is introduced.

Just a reminder to check that enterprise will not pay this charge as they have been known to pay and bill hirer. Check the contract would be advisable.

Nothing unusual about an appeal being turned down by the parking company they just want the money.
Appeal to IAS just to show that the Registered Keeper is engaging with the process. Don’t hold your breath this will in all probability die a slow death in the fullness of time.