Confirm what Alan has just said.
I got back from Oz 10 days ago and CASA are only issuing temporary certificates that last about 2 months (mine started on the 8th Dec and ended 31 Jan) and to validate this, I needed to just take a check flight with an instructor. Next time I go back, I have to do the whole thing again.
Basair were very good BTW, but their check out included a Nav trip. Another FBO in Victoria were less concerned and simply wanted the usual check-out.
The only other alternative is the full Oz PPL.
I ended up taking an instructor from Basair to do a flight around the Harbour Bridge (a must) and then went in-country to Victoria and a small FBO did my check-out and I pootled around there.
Flying there is probably more stress-free than the states and a C150 was about £40ph wet.
Have fun!