Yep Luke is right imo. Do exam questions! When i started doing checkpoints i didnt even know how to approach a few questions, either because we hadnt learnt aobut it or it was a question that ive never seen before.
This is the best way to prepare for the exam, the more exam questions you do the less likely you will be thrown off by a question. Ive also noticed that they use a lot of similar question structures 
Yeah, our textbook is fairly summarised (StudyOn), and our teacher doesn't use anything AT ALL apart from this book. Furthermore, I think some of the things are more applying your knowledge more than anything - which is something they definitely do not teach from the textbook.
This is where the problem lies...
I was planning to read that textbook... Do you reckon i should or is it a waste of time?
Hmmm, I wouldn't bother. There isn't much/if anything it can add to Heinemann, it's basically a summarised version of it. Better off learning Heinemann, it has everything you need to know.