They say 'where your vehicle is parking it is permitted to stop for as long as is reasonably necessary for the purpose or picking or dropping passenger however you are not allowed to leave your vehicle there.
This is total tosh. There is
no legal requirement for a driver to remain with the vehicle when carrying out boarding/alighting activities. You were engaged in what is called "assisted boarding", which involves collecting a vulnerable person from a safe place and escorting them to the car to board. The same applies with alighting.
So if it were me, I'd be taking them to adjudication. However, please do as CP8759 asks, and post the documents.