I skipped the Unit 1/2 when I did biol 3/4 this year. Here's what I used;
A+ notes (very useful for general summaries of all required knowledge. Includes mind maps for visual learners)
Biozone (incredibly useful)
Nature of Biology (it's your standard text book I 'spose)
But really, in terms of getting the leg up, the thing that helped me this year the most was sheitloads of practice exams. The thing is, as the course is fairly knowledge based (as apposed to skill based) after a while of doing all these practice exams, you're unlikely to come up with any thing you've never seen before. In particular, I recommend, NEAP and Lisachem past exams. Insight are ok, but the answers are twice as big as the exams and tbh, sometimes not all that helpful.
I would definitely recommend A+ notes and Biozone. However, with Biozone, make sure you fork out the extra 10 or so dollars for the model answers. It makes things so much easier to check your answers. As far as text books go, NOB was meh. I'm sure any textbook would be sufficient enough tbh.