I'd consider wheather you want to end up working back in the UK or not in the future, you'll find it harder to convert Ozzie to JAR than the other way round and more expensive, you'd also have to have a shed load of hours before most employers in the UK would consider you as you wouldn't have the local weather experience that comes with flying in the UK.I'm not saying you don't get challenging weather in Oz because I'm sure you do, but employers will think 'oh he's just been getting a tan on the Gold Coast' how's he going to cope when it gets a bit crappy i.e like it has lately.
Why not get a JAR CPL then convert to the Ozzie licence, I'd have thought that would give you more options in the future.