From your previous experience with loading/unloading cases, are councils lenient with proof of weight, photos of the items tht were unloaded etc?
Councils are never lenient, because they get the PCN money if they reject representations. The only unbiased place is the adjudicators at London Tribunals. So the bottom line is that if you want to stand your ground rather than cough-up, you have to be prepared to take the council to London Tribunals. Of course you have to risk the full PCN penalty. If you win you pay nothing, if you lose, you pay the PCN penalty, but there are no additional costs or charges.
However, first you have to go through the process, so must be rejected when you submit representations against the Notice to Owner. Of course they may accept your reps and cancel the PCN !