As mad_jock says, you need an ICAO PPL to start your ATPL groundschool.
When it comes to distance education vs classroom learning, it depends on your learning style. If you are focussed and disciplined then self-study is fine. I am doing my ATPLs with Bristol by distance and passed the first 8 with good marks. A classroom revision course is compulsory before the exams (for Bristol is two weeks before each set of exams) so you get handouts, practice exams, etc then. If you are enrolled in a distance education course the instructors are often available by email or phone during the self-study period and there are online forums where students can share questions and answers.
Also (CharlieTangoZulu) make sure you consider how long your exams are valid. For JAA/EASA you have 3 years from your first exam to get your CPL/IR if you want the exams to count towards a "fATPL", so make sure you have the money and time to get everything done in time before you start. I'm envious of you being in Perth - would be some awesome flying if you got your PPL there.