template letters on the cab website – follow link in earlier reply. but this is what CAB say
If you get a ticket
If you get a ticket on your windscreen or through the post, and you think that it is unfair because, for example:-
you didn’t break the rules
it wasn’t obvious what the rules were, either because the wording on a sign wasn’t clear or there were no clear and prominent signs about the car parking rules, particularly at the entrance to the car park
the charge you are being asked to pay is too high. Legally, the amount charged has to relate to a calculation of the loss to the landowner. They can claim for lost income if you occupy a space that someone else could have paid for and used, but only if the car park was full and there were no parking spaces left. For example, if parking cost £1 an hour and you have been issued with a parking charge notice for £30, you would need to have parked there for 30 hours to justify the charge. If you challenge the ticket because the amount charged seems too high, you can also ask for a breakdown of how the landowner’s losses were calculated
the ticket has been sent to you as the registered keeper of the car, but you were not the person who parked the car at the time the ticket was issued
you had a good reason for breaking the rules, for example you may have stayed over the time you paid for in a hospital car park because your appointment overran