As I understand it with grants is, you are offered an award amount (£x), along with a catagory (size) of vehicle they are willing to fund and a short list of vehicle’s them deem suitable for your needs. This forms the basis of your needs. You can choose any vehicle in the catorgory you were awarded, which doesn’t need to be on the list up to the value of the award plus 50% from your own funds if needed.
The amount you are able to contribute towards an advance payment is limited to £750 or 50% of the award, whichever is the least.
From Motability Foundation FAQs section:
“The majority of beneficiaries will not choose to make any contribution on top of their Advance Payment grant, however, if you choose to order a vehicle that costs more than the agreed grant award, then we may contact you to better understand your requirements.
If you choose to make a voluntary contribution towards your Advance Payment grant, there are limits within our policy. Grant applicants can add up to £750 or 50% of the Advance Payment grant, whichever is the least.”