This may help, applies more to Tesco's or Sainsbury's type car parks.
To whom it may concern
[Add their title and address, Miss Jones}
I am in receipt of your letter dated [insert the date Miss Jones] alleging that a vehicle registered to me overstayed an arbitrary duration in a vehicle park attached to one of your stores.
As I am sure you will be aware, it is the driver of the vehicle with whom any contract to park was made, not the Registered Keeper. You will also be aware that the terms of any such contract must be set out in such a manner as to be obvious to anyone with whom you wished to make the contract. These terms must comply with all applicable contract law, such as the Unfair Contract Terms Act 1977.
Should you wish to pursue this claim, please supply evidence that the person parking the vehicle you allege to have overstayed the set duration would have had the opportunity to read the contract terms. Such evidence must be, as a minimum:
a detailed route and timings of the vehicle's travel into and through the vehicle park;
a detailed route of the driver's passage out of the vehicle and into the store - this and the evidence listed immediately above are to show that the driver had reasonable opportunity to see and read the contract terms;
photographs of all relevant signage in situ in locus in quo at the time of the alleged overstaying so as to show that the signs were actually readable;
an accurately-drawn, scaled, map showing the location of each sign and indicating which you believe the driver would have had the easy opportunity to read (the routes of the vehicle and driver should be superimposed upon the map);
details of the weather conditions at the time, in particular the visibility (all to be confirmed by the Meteorological Office);
sufficient details of the driver with whom you claim to have made a contract to enable their unique identification;
a detailed description of the processes followed to record and analyse the evidence of the alleged overstaying; and
a notarised statement from a senior manager at the store to the effect that your recording and analytical systems were working normally at the time of the alleged overstaying.
Without the above, I cannot entertain your claim and any further demands for payment will be considered harassment and will be reported to the police with a view to your criminal prosecution under s1 of the Malicious Communications Act 1998, s85 of the Postal Services Act 2000, s127 of the Communications Act 2003, and/or s2 of the Protection from Harrassment Act 1997 - this last with a view to the court issuing a Restraining Order against you. Additionally, civil action will be taken against you personally and your employer to cease and desist and for the recovery of all costs, together with a substantial payment in compensation for the mental pain and suffering caused.
I expect your reply by return, either providing the evidence requested above or indicating simply your termination of this correspondence.
If you get a ticket in Sainsburys, Tescos etc and send that letter, expect a world of pain.
Responding to any communication from a PPC marks you as a fish and they'll harrass you for ages.
Completely ignore anything they send to you. I really can't stress this enough. Never, never, never write to them or call them. They'll send 4-5 letters then give up.
If you communicate with them they'll hound you for a lot longer.
There is no reasoning with them. The points in that sample letter are completely valid, but the PPC has no appeals process. They know what they're doing is a scam and nothing will persuade them to stop harassing you, other than completely ignoring them in the first place. You have a 1 in a million chance of them ever taking you to court.