Richard, I am sorry and disappointed to hear that you have been messed about and treated with such a lack of consideration and understanding, by a body which was set up to exclusively meet the needs of the disabled customer.
There is a need for Motability and DL to have a joint file on the person with their needs, so that they can react accordingly in times of an emergency, rather than just treating Motability disabled customers, just like any normal customer.
Sorry I do not have any personal experience or advice to pass on to you, but hopefully there must be people who have been in the same situation as yourself on this forum, who can help with passing on their experience and advice.