Just been down to the dealers and low and behold they will only require the reduced AP at the time of hand over, so good advice and happy days. There may be people who feel that it is not possible to ask the dealer for any deviation in the AP at the time of handover, let them know your feelings and stand your ground, any difference is better retained by the new owner rather than the dealer who does nothing to support you through changes to the system.
Neil,
The AP paid isn’t retained by the dealership per se.
It is ultimately passed onto Motability (minus comparatively small Motability handling fees).
Although a few years old, the following thread explains the Motability handling fee: