Thanks for getting back to me, that's useful to know. Really, I can't see how a 3m wide drive would work for a double garage on a street front block.Yes for a double garage. But the retained dWelling has no garage.
The R-codes seem to deal a lot with side access to a rear dwelling but not much about street front access development except "no driveway wider than 6m at the street boundary". So it seems your drive for double garage on a street front block can be anywhere between 4m and 6m as long as it is .5 from a side boundary.
The development I want to do has a house behind a house and I am hoping I don't have to go wider than 3m. I have 3m clear, but not more than that.