You are dealing with a firm of ex-clamper thugs who are members of the ICP. No matter what you put in your appeal would have been rejected. Nothing new there.
Personally, I don't advocate appealing to the IAS as it is a kangaroo court and you have almost zero chance of winning an appeal there either. Others may disagree.
You are now in a state of limbo. Should NPC try and take this all the way to court, you have a very good defence in
Jopson v Homeguard [2016] which is a persuasive appeal case where the judge defined that stopping for a short period to load or unload is not parking.
The images show that they were taken by an operative, not ANPR. The sign appears to be hidden behind a tee or a bush. There are flaws in the NtK that breach the new joint Code of Practice (CoP) that can be used against them too.
If you feel that you want to waste your time on an IAS appeal, you should use the new
joint CoP to see where they have breached their own rules, especially the 21 day restriction on appealing to the IAS.
Once that is rejected, you will receive a load of debt collector letters which you can safely ignore. They are powerless to do anything, no matter what they say. We don't need to see them.
At some point, they may/will issue a letter of claim and then a claim itself. That is good because then you can have a truly independent arbiter, a judge, decide whether the keeper owes NPC a debt or not.