Gidday,
I did my conversion in July 2009. I used AFT for the theory side of things and Ad Astral for the flying side of things. It is hard work but the exams are acheivable with a bit of work. I self studied for around 3 months using the AFT materials and then had two weeks in Perth in which time I passed CPL LAW, ATPL LAW, IREX exams and completed the IR at Ad Astral. The biggest stress that I found was dealing with CASA and ASL. Make bloody sure all your paperwork is in order before you go to Oz, you need a certificate of validation issued before you can under take the flight test and mine took 6 months to be issued after a couple of lost applications etc. With ASL just beware you can't book all you exams at once, you have to pass the CPL law before the system allows you to even book ATPL Law and you have to pass both law exams before you can book the IREX exam, in Perth there is only one exam centre so it can limit your options. It was probably the most stressful two weeks of my life for a long time but is it possible, you have picked a great training school in Ad Astral, I would recommend AFT for the theory and practice exams with Bob Taits instrument rating study guide for the IREX and allow youself 3 months self study before attempting the exams. Good Luck!!!