I'm not sure how the system works in Australia as we've ended up having my son diagnosed and doing therapy in the states... but can you get started on any therapy before the diagnosis? We do floortime with our OT and I think it's fantastic. I just bought Engaging Autism to read up on it and it helps you start it yourself. The beauty of floortime is it recognises that the parent is a child's best teacher so it's really about educating yourself and using floortime in your daily life.

We are also recovering our son with the GAPS (gut & psychology syndrome) protocol, which I'd highly recommend too. I love that we're not just treating the symptoms, but the cause, and our son will actually be free of autism one day. He used to have severe anxiety and going anywhere was very hard for us too. He goes to a developmental preschool now and I have no problems leaving him at all. He rarely has anxiety these days.