Now here comes the point of difference. I think you are saying (and I apologise if I am misunderstanding you) that optional extras ordered by the customer (which was the specific question that the OP asked) are subject to VAT unless the person is exempt due to the reasons given earlier. My understanding (and I’ve never read anything to the contrary, but am happy to be shown a link that suggests otherwise) is that this is not the case. If the person is a full time wheelchair user and needs a substantial and permanent adaptations, a private buyer can get the VAT off the total price of the car including all optional extras, regardless of what those options are (bigger alloys, sunroof etc). However, the same person (who meets the HMRC criteria) ordering a car through Motability still has to pay the full price of all options, and does not get the VAT knocked off. Happy to be proved wrong, although it’s more for the OPs benefit than mine, as we are buying privately so will enjoy the full VAT exemption!
I believe you are right or more right than me, as I assumed and only assumed that, if someone met HMRC criteria, they would automatically qualify for exemption on any factory or dealership options on a Motability lease and apologise for any confusion caused.
My question now is, Why and has anybody ever tried it?