Appealing to the parking adjudicator
If your formal appeal is refused by the issuing authority you can appeal to the parking and traffic appeals service.
The enforcing authority should send you an appeal form with their notice of rejection. If they do not you should request one.
An appeal will involve the issuing authority in a lot of work because they will have to produce a tremendous amount of evidence including a case summary, copies of the penalty charge notice, enforcement notice, all other correspondence, colour images of the offence and the traffic management order.
You will need to decide whether you want your appeal decided on a postal, personal or telephone basis