I was thinking the same thing, Nearly. I think there's potential mileage in Article 5(3), but has the gentle approach been tried? First, establish an answer to Nearly's question (e.g. does the presence of the car merely reduce the available width of exit for a relatively small number of people, or does it stop the doors being opened at all?) Could the car be parked back a couple of feet to allow the door to open (controlled perhaps by some bollards) and, if so, would there be sufficient width? Is the door actually required for means of escape and, if so, for how many? Does the commercial premises have a legal right of access over the land that is also the parking space and over the land beyond? Is the neighbour out to cause a problem or would he/she be happy to co-operate? Have there already been negotiations with the neighbour? Is the neighbour aware of the problem being created by the car (is there a sign on the outside of the door, for example)? Out of interest, what was there first - the commercial premises or the car parking space?
Stu