I think Motability would be more likely to offer you an extension of lease upto 5 years on your current car, than give you a grant, particularly if your current vehicle is still suitable disability wise. Fuel cost isn’t a consideration with grants as Phil has pointed out above, thus any grant would probably be for a standard diesel as opposed to the more expensive PHEV varient , so you may be back at square one with fuel cost. Another way maybe to see if you maybe able to get a grant from a charity other than Motability. For example if you have served in HM Forces, there are a multitude of ex-service charities who maybe able to help. Or is there a charity specifically connected to your disability? Or search here: https://grants-search.turn2us.org.uk/
Thanks for the reply diesel is not an option our journeys are mostly 5 miles or less but frequently several times a day. Modern diesels have DPF’S fitted and the filter will block up with short journeys, the vehicle will then need to driven at a constant speed without stopping to clear the filter. Our last car was a diesel, and we had a nightmare with the DPF. I have spoken to turn2us about a grant before I don’t qualify for help I tried for a grant to buy a scooter and was turned down.
Yes I agree about the extended lease I wish I had not used our car as deposit and sold it privately.