Carl sadly it is very hit and miss with dealerships and being a motability customer. Some are great and treat you like any other customer. But some just act like pure snobs and its like what do you want. And drop the whole sales pitch etc. When I had the bmw 1 series previous to my current car, my local dealership didn’t show a care in the world about my custom. So I went to the next dealership 30mins drive from where I lived and they was amazing, give me the keys to a car to go test drive on my own and just said you got about 30mins so go enjoy the car and if its right for you we’ll go from there.
Hope you manage to get the dealership to honor the original AP but if not I’d just walk away and find another car you like at a decent dealership that either has a car in stock which you can have pretty quickly or place a new order.