In answer to John's post. There is no offence under Protection of Freedom Act 2012 which covers private parking as the act refers to parking charges. The most the Private Parking Company (PPC) can request is the parking charge which will be about £1.
All the rest is a penalty and the PPC cannot charge you a penalty. The next question is whether the LL has a contract between the PPC and the LL allowing the PPC to take you to court on behalf of the LL. Unlikely this will exist and you are perfectly entitled to request a copy. The LL can claim damages, but if you were shopping and enriching the LL the damages will be zero. The LL is wholly responsible for the actions of their agenst the PPC.
Parking Eye has taken many people to court and won as the people have ignored the summons, however in every case where it has been defended, they have lost. If by some remote chance you lose in court, maximum costs would be about £50 plus the parking charge of about £1.
Some PPCs try and state that the penalty and extra parking charges are because they erected signs, monitor the parking, employ people etc but the Appeal court, (Parking Eye vs Somerfields) have ruled that these costs are part of the running of a business and were thrown out.
You can appeal to POPLA which will cost the PPC £25 however POPLA is managed by the BPA so you may lose, but their decision is not binding as they have no legal status. In the meantime carry on ignoring all their demands for money even if you get one from a Graham white solicitor unless of course they send you a summons from Northampton Court.
If you defend based on unreasonable charges and whether they have the authority etc request for it to move to a court near you and complete the allocation Questionaire etc. If you are defending and have a good defence, PE will withdraw, but check with the court that they have and do not believe PE or the relevant PPC.
BTW just to throw a spanner in the works, contact the local council and inquire whether the PPC operating on the car park is paying business rates to the council or whether the LL is paying their business rates. That should raise some interesting questions.
Hopefully the above is of some interest.