HMRC are great for two things, paperwork for no apparent reason and ambiguity. It’s in absolutely no doubt you’ll have paperwork to deal with for just about everything they can potentially require. Unfortunately you need someone who has dealt with this specific matter on multiple occasions as expertise in VAT exemptions comes from trying and succeeding AND failing and learning what consistently works and what doesn’t. Anyone can read and try to interpret the wording, even an expert in HMRC language could come up with a relatively decent guide but that’s no guarantee.
That’s a lot of words for ‘if you haven’t done it successfully, repetitively, then it’s an educated guess”. Some may be able to tell you what worked for them but you may have complexities, especially trying to separate your funds from the grabbing b&st&rds that’ll happily take all your savings for care. If the dealership can’t help, maybe there’s someone within Motability who could advise or it’s that long wait on the HMRC phone.
I'm Autistic, if I say something you find offensive, please let me know, I can guarantee it was unintentional.
I'll try to give my honest opinion but am always open to learning.
Mark