Spent a year in Australia 2007-2008. Had a working holiday visa. Worked 4 months on the Great Barrier Reef - an island - and travelled quite a lot. Went with my girlfriend, and she has close family over there who gave us base camp etc.
With your trade, I bet you could find work easily, building trade is massive over there, and all the mines need workers. I'd love to go back.
On the visa thing....we were under the impression that once you have had a one year working holiday visa, you can't get another, unless, you do 3 months rural work (fruit picking etc) and then that allows you to get another years as you're helping the country etc.
Now....I love travelling Since July '09, I moved to Southern Ireland to work for a games company which is f****** brilliant and amazing experience. Giving me the opportunity to travel more too.