G'day Maxx,
In summary,
You'll need to do the 14 JAR ATPL exams in a JAR country. UK would probably be the logical choice.
You'll also need to do a Class 1 medical, again in the UK. It must be done at Gatwick.
Don't know if your turboprop time is multi or single pilot.
If single pilot, now only have to do an abbreviated IR in the UK. Min 15 hours I think. Check on the CAA's website.
If +500hours multi crew and the type is multi pilot (eg Dash 8, Saab etc) then all you need to do is a initial IR check ride on
that type you have +500 hours on with the CAA onboard (sim or aircraft observing.
You can do the study for the exams distance learning in Oz but the brush ups must be done in the UK. I'd recommend Bristol.
Have a look
here for more detailed info.
Note: The CAA have changed the 50 hours IR requirement.