You can order from any Motability authorised main dealer and still have the car serviced at your nearest main dealer. Personally I see no sense in not having the car serviced at a main franchised dealer. You aren’t paying and they know the cars best, use manufacturers parts, are aware of recalls etc. If the location isn’t convenient get them to collect the car and return it to you after service.
im being charged for a pick up and return as my dealer is outwith their service.
If I understand you correctly (‘outwith’ is a Scottish expression that isn’t used elsewhere ?) your dealer does offer a collect and return service, but it isn’t complimentary? If that’s the case, I presume that Motability were happy for the cost of that to be paid for as part of the service? For many disabled people it wouldn’t be practical to have a courtesy car or to hang around at the dealership for hours.