As I understand most plumbers in Australia work either for themselves or for a plumbing company earning a good wage.

If you were to work for in a permanent position (let's say 45h/week) in an manufacturning plant what would you consider an appropriate hourly rate?

there are minimum wages set by each state, see:

http://www.workplaceauthority.gov.au...pay-scales.asp

It seems $19.71 is the minimum hourly rate in Victoria but there are generally extra allowances on top of that.

Somehow I don't think I can find a plumber to work for anywhere close to minimum hourly rate.

That might have something to do with the amount of :- business insurance premiums paid, training, licensing, registration fees and compliance certificate costs that are added on to the end of the hourly rate not to mention vehicle and travel to & from site costs

no because he would tell you to shove it