Most dealers have no problem if the AP reduces, read the posts on here.
They don’t have to cancel and re-order the carat all, it’s only the Motability paperwork that’s re-submitted. It only takes about 10 – 20mins and it costs the dealer nothing at all to do it.
Please excuse spelling/typos. Apart from being a clot it turns out I had one on my cerebellum that's now causing various problems!