you will pay the ap at point of order unless you have an agreement with the dealer
Not necessarily. Whilst it’s always best to get the dealer to agree to this approach at the time that you place the order, many dealers will be happy to adjust to a lower AP (if it happens). It’s a 5 minute admin job on the Motability system that doesn’t affect the actual vehicle order.
When we ordered our last BMW, the AP dropped just £150 the month after and the dealer amended it without me even asking! They said to me “that £150 is better in your pocket than Motability’s”! If the dealer says that they won’t do it, and the price drop is significant, I’d tell them that I’ll be cancelling the order and placing it with another dealership. Given the state of new car sales at present, I suspect that they will very quickly change their position!