contact motability and tell them what hes said and they will tell you what it will cost if anything to change.
ive just had to change 2 years 4 months in as my back wont wait till sept, for something easier to get in/out of. they can charge up to £250 to change early they charged me £50. but i will get a pro rata refund for the extras i paid for and the gcb.so iam getting just shy of £500 back which means the new car isnt costing much as its a lowish ap and the dealer had a £500 contrinution offer.
but all are discretionary its simple to do and so long as you have a valid reason and arent a serial early changer there should be no problem.