My father was a mechanic (for Cyril Williams, Junior TT winner) in Wolverhampton, using petrol to clean engine parts on military vehicles. I believe from what he told me that some might have been left over on occasion... He also, incidentally, drove in the occasional convoy, trying to keep sight of the lorry ahead in unlit roads, with shielded headlamps, and no roadsigns. (Only the leader knew the way).
I assume the many garages which were engaged on war work of that sort were more generously supplied with fuel. So I'm sure there would have been some 'left over' - although if you were on the road in a private car once 'basic' had been withdrawn you needed a 100% cast-iron reason to be doing so, probably in triplicate, as you'd likely be stopped by Plod or the MPs.
Convoy work of that sort is depicted in the 1943 movie The Gentle Sex.