Get your PPL and build up your hours. By the time you have got a good 175 hours in your logbook, you can decide whether you are going to stay in Aus in which case do the Aus CPL, or if you are going back to the UK in which case do the JAR training and exams when you get back there.
There is absolutely no point in doing the Aus CPL unless you have residency and then "converting" it, trust me the two ways of doing things are very different and you will have to do so much of it again you may as well do it all there rather than try and unlearn stuff.
Trust me I've done both CPLs and instructed in both countries. Good luck!