Hooligan,
Surely if the instruction is "Give Way to A300 coming from the right" then that is a mandatory instruction which must be adhered to-not a case of I reckon I can nip out in front of it. I can't believe the instruction would have simply been "Give Way"-can you?
In aviation terms the controller is issuing an instruction that the other aircraft has, as you say,priority and so far only you seem to find ambiguous. There is also the major difference with the roads in that here the controller makes the decisions at junctions,not you the driver!!
I also can't believe that you would prefer the instruction to be "Stop until the A300 passes" or would you?
I stand to be corrected here but if there is a general mis-understanding of what "give way" means then there are lots of ATCOs at airfields who had better keep a b****y good eye out.