Hello
Not sure of Qld as a whole but all training to gain licence in Brisbane area is to be done over the net. south Australia run a class room course. Not sure about other states.
Like in the UK the money plumber's can earn is vastly exaderated. I'm earning about $29 an hour. Get extra for working on Live sewer and for working in the rain.

I have come across licenced plumbers earning between $21-$34 dollers an hour (Qld).
Plumbing is very diffrent and fisically harder I have done sheet metal work (Guttering) roofing, lots of digging, septic tanks. Alot of the work is out side which is nice but I've not had a summer hear yet.
Gas fitting I'm told we'll be able to gain a licence straight away. as it is very much the same as in the UK.
All the bets John