Hi
First thing dont panic and pay unless issued by a local authority these are not fines but parking invioces.
Usual advice is to use the appeals process first if nothing else these delays the parking company form escalting the charge.
Lots of online information and advice especially on Martin Lewis money saving expert site and pepipo forum.
All though I dont know the full ins and outs I think you would be able to challenge this quite easily, I have never paid a parking charge that has involved a person with a disability.