If you’re getting a car then I’m assuming (correct me if I’m wrong) that you are able to get in a car and get out of a car and walk a certain distance.
What is stopping you travelling to the dealership and collecting?
Can a friend or family member collect for you? Also I can’t understand why you think that you’re not getting a car. The order will be confirmed by Motability. If you’ve lost your paperwork just give them a call or call the dealer to confirm that the car is on order.
HTH