Well I think that is the point of the include miles/period. If you take it in Jan they should do B,D and C,G,H,I because they will be within 70 days. I'm surprised it isn't 90 days to be honest, at least that would limit you to 4 visits maximum per year no matter how out of sync things got.
Plus don't forget you do have ultimate say in it, it's your car - I would wait until Feb, get B,D,C,G,H,I done and then you can also get your MOT renewal done without changing the renewal date (you can have up to 30 days overlap). One visit.