I'm in a similar situation now. Don't worry about it!! Superb the advice I have been given on here.
It would be a civl case so they have to have had hard evidence that you broke their implied contract as they can't issue a
parking ticket
. Only the police and people working for councils can do that..... like traffic wardens.
Picture of the the driver?
Picture of your car?
Picture of your car windscreen with no ticket displayed in your windscreen??
Innocent until proven guilty??
Best thing to do is to do a serrch on excel parking in the forum, and read it all. Then make your own mind up.
Needless to say im my situation I have asked them for some evidence to prove my guilt that I have not purchased a ticket/have and invalid ticket and will be ignoring any threats I get though the post and storing them up as evidence incase they decide to goto court. You may be able to use the letters they send you as evidence of harrasment and fraud.
Good luck