From memory 2.4m wide is the minimum in the Australian Standards on parking spaces. That would be an impediment to changing the status of the space formally to a parking space. However, a ‘storage space’ is for storing stuff you own when you are not using it elsewhere. You own your small car. Why not ‘store’ it there when you are not ‘using’ it elsewhere?
I assume the ‘storage’ space can be readily driven into and it is adjacent to designated parking spaces so it would not look odd to have a car there?