I would email the cheif exec’s person again – explaining you have heard nothing from them as promised.
However you did have a text on “date” from europcar saying the hire car needs an mot and Motability are looking to get the hire car changed given the state of it, Although you have heard no more about a change of hire car since!
Explain the latest development of the car needing an MOT, which required you to chase it up with Europcar, only for them to say they want you to arrange MOT with kwikfit drive there, which is a 60 mile round trip and should it fail you are stranded awaiting for a taxi to be sorted, which is not on.
Just go onto say your not happy with how things are unfolding at no fault of your own and wish to be placed in a suitable hire car within the next 48hrs untill June as promised……