Hi,
From memory the form I provided a link for was sufficient for the dealer at the time, I dont think the dealer I was using was that arsed to be honest, as long as they had a declaration from us on the form it was sufficient for them and to be fair when are the inland revenue ever going to check? especially given that the inland revenue itself cannot provide a specific guide for what dissability or what mobility/ driving aid and meets the criteria for VAT relief.
Some dealers ask for a seperate declaration from the person applying for the VAT exemption this can be in either a written declaration or a generic one like the one on your link, or at least that’s how it was when I last appiled but that was a few years ago.