How do you know they have subcontracted the work out - and if so - do you know to whom ?
You could try and chase up the subcontractor
If the car has failed its MOT, it is not roadworthy & it cannot be used, or moved, except to somewhere to do the necessary rectification work.
You cannot (legally) take it home, take it out and 'go to work' or, do the shopping using it. It can ONLY be used to go to the repair shop.
If an ANPR camera sees you driving an MOT failure you'll have a 'bit of trouble' knocking on your front door.