In response to Masky and Kezo, Motobility are correct in what they have said to you.
What you have to do is view ordering a new car through MB as two separate processes. We choose our car and accept the AP is, say, £2500.
We see the dealer who opens his screen on the Motobility page, checks our eligibility etc and then accepts our MB order at £2500. That’s the first order and generates a reference number
The second order is when the salesman puts a hold on a build slot or on a physical vehicle on his dealership intranet. That’s the second order and the two are linked.
He can cancel and reorder the MB order without cancelling the dealership order. If he doesn’t, he’s just being awkward. My dealer didn’t even blink, he said good job saving £500.
MB can’t interfere in Part b but you can. Think about it, the car he ordered you is still there or scheduled to be built. He could be an arse and give it to someone else if he has a customer on hand or he could spend 5 minutes on the computer changing MB order, keep the sale and have a happy customer.