Pretty sure the Open Polytech of NZ have a course of study you can do - can't remember the costs off the top of my head, but it follows through systematically towards what you need to cover - oh and study a shitload of codes, regs, OSH stuff.   You should ask around your area, or put up a notice at the merchants and try to get a study group together of anyone else looking to sit next year.  It really works if you meet every couple of weeks and ask each other questions -old exam papers are a good route to follow as well.