Hi Rich, You will struggle to acheive what you want sorry.
The grant award plus 50% is the maximum they will allow using the grant. So your limited to £1499 end of unfortunately.
Ditching your grant award, will allow you to have what you want on the scheme (funds allowing) or buy private
A third option that might work, is looking in the Motability offers and cashback topic and seeing if there are any AP contributions. I know some Hyundai dealers are offering an additional £750 off the the AP or as cashback on the 5 and 6 ontop of the NVC. Whether this will work, with the grant or you can come to an arrangement with any dealer I don’t know but, maybe worth a try.
Have you put a complaint in saying the grant award won’t enable you get a vehicle suitable for you health needs. Pigs might fly but, worth a try!