OP, the situation is actually straightforward.
The demand for payment of the penalty charge was made upon the lease company;
They made reps as they were entitled to do under the grounds of 'we are a vehicle-hire company and the vehicle was on hire...';
UNTIL the council formally accept these representations - and you don't know they have, for all you know someone in the council offices pressed the wrong button and issued a demand for payment from YOU AS WELL - then the council may not make a demand from you.
And you are an AS WELL and not an INSTEAD OF until the first demand is cancelled formally.
Your reps I suggest would be along the following lines:
Penalty exceed the .......circumstances of the case' these being that:
1. You have checked with the keeper(****leasing company) and it is clear that the authority had not served a Notice of Acceptance of Representations on them before they served their additional demand for payment (PCN) on you. If you have been misinformed on this point by *** then the authority simply need to include a copy of their NOA with their reply.
2. The hire agreement and other mandatory details supplied by *** to the authority in support of their representations did not comply with statutory requirements and therefore the authority were not empowered to issue a PCN in your name. .....is the point being made in the references above and if Hippocrates has already identified the discrepancies then I won't reinvent this wheel.