It’s not a case of telling the truth. No one is suggesting you lie. However, there is a difference and admitting liability when there was no reason to do so and thus throwing away the “golden ticket” is not the way forward.
By being “truthful” instead of being sensible you have now prolonged this matter and are likely to have to defend this in court if you honestly believe that you’ve been wronged.
All you had to do was appeal as the registered keeper of the vehicle and this would have been over. NCP had no idea who the driver was until you blabbed it by being “truthful”. Because Gatwick airport is land under statutory control (bylaws) the Protection of Freedoms Act 2012 does not apply and therefore there can be no Keeper liability.
There is no legal obligation on the Keeper to identify the driver to an unregulated private parking company and no inference or assumptions can be made. The burden of proof was on NCP to identify the driver but you have simply done the job for them, instead of leaving them with no choice but to cancel the PCN.
So, you’ve been asked above to provide a copy of the NtK but you don’t appear to be reading or noticing the request above.
https://www.ftla.uk/private-parking-tickets/read-this-first-private-parking-charges-forum-guide/