The £750 is, as far as I am aware, definitely a one-off. If you had it previously I would expect you wouldn’t get it again. It might be worth asking Motability though as you returned the previous car relatively quickly so there may be an exception I don’t know about.
There’s always the possibilty of a grant too, although that is a whole other set of hoops to jump through.
"Man is born in freedom, but he soon becomes a slave, in cages of convention, from the cradle, to the grave."