Hi Danny
I can only comment on mining.
It is hard for anyone to break into mining at the moment as there have in the last 12 months been a number of redundacies in the mining industry. So your chasing jobs up against people with experience.
The issue is your visa. I believe you are on a WHV. This is a major problem. You can only work for an employer for 6 months. Inductions for mining companies can be a month. Training is then upto a couple of months. So, with only 3 months of actual work, it isnt worth it for them.
There are also issues with mining in QLD. Most of the mining is coal and this requires very particular tickets, without which you can not enter a coal mine.
Lastly, there are issues with being a plant operator. It isnt the same as the equipment used in mining - a face shovel might look like a normal loader, but a normal loader can be fitted into the bucket of a face shovel!
The main industry job site is infomine.com and go to the careers section.
Good look with your hunt.