Hi all,
I'd just thought I'd chip in on what I did during my Summer holidays.
For chem, I completed all the Revision chapters from Year 11 in the Year 12 Chemistry Book - I'm not completely aware of the study design changes in terms of what Revision Material will remain the same, but I assume that generally, the first ~5 chapters will remain the same (in no particular order, topics covered include revisiting redox, stoich, learning gravimetric and volumetric analysis [applications of stoich] and revising acids and bases). I also read ahead in terms of Chapters 6-8, which, under the old study design, were instrumentation techniques. I am aware that this has been moved to Unit 2, so I'd just read ahead on the topics replacing chapters 6-8. Once I get ahold of copies of the 1/2 and 3/4 textbooks for the new study design, I'll be able to better inform you on what I recommend you do.
I found that this significantly reduced the worry early on when school starts again, and definitely helped in me overcoming and managing my workload throughout the term.
Hope this helps in anyway (soz old study design haha) and all the best in everyone's studies for 2017!