Jord, here goes now listen.
You are well ahead of all the others your age just in your thoughts alone.
OK you have an idea now what you want right, everyone has told you the different ways of going about it. Good TEE results won't get you a trade. Finish this year, maximise the work experience program through your school. If someone likes what they see you may land a job just from that(highly unlikely, But never know).
Apply for all jobs in the paper which start around October-September ready for the January intake of apprentices. Still no luck, don't worry instead of year 12 use that year to go to TAFE and do a pre-apprenticeship.
I will guarantee you'll land a job when you finally get the opportunity to show a potential employer what lengths you have gone to. Plus you will cruise through your trade with confidence as you will already have the the basic skills and work place enviroment awareness. Safety is a major concern for companies these days, you will be more in touch with the hazards than some punk just out of year 12.
This was the process I took. I've never struggled from not going to year 12, I have friends that went all the way through to uni (still paying it off) and earn half my wage and still unhappy with their work.
Good luck mate, try get with a big company. It can be dangerous work and they take safety policies more serious