I don't think last years was 82 (I'm assuming this from personal experience) and there is no data for 2016 maths 2u on rawmarks index. Just by having a glimpse of the paper I can see that it was harder (haven't come to the conclusion of how much more difficult). I'd say the cutoff would be 80, but it honestly depends on the cohort and how all 2u students went. If you've done the 2013 past paper, make an unbiased judgement on whether you thought your paper was harder or not. If yes, then you can expect the b6 cutoff to be below or around 77 (I gathered this data from rawmarks index).
Best of luck!