Sal,
Where in Brisbane are you? The Royal Brisbane & Womens is the major public hospital but I think you do need to go to the hospital who's catchment area you are in. Your GP doesn't sound very helpful unfortunately they are probably the ones who know which catchment area you belong to. Alternatively you could ring RBWH and make enquiries, they have a birthing centre there that I run by midwives. RBWH number is 36368111.
HTH