talk to your solicitor , they requested after xmas for the move and you have stuck by that " which was good of you even though convienant" the deal has been made and therefore you want closure .
storing a car is much easier than housing people and property and a lot cheeper to boot.
Resentment will be felt if either side pulls out but facing being homeless is far more worrying than any garage.
There is nothing wrong with asking to finalise the deal and wanting to move in . as it is still a buyers market and everything barring the finalising of the deal is done , it is now up to them to get moving if they actualy want to sell this property .
They are holding you up not the other way round. with this in mind a cut of point should be arranged and soon if you are to not face further unwanted expense