Hours a day? That's a toughie. I always used to just end up doing it because I enjoyed it (now exam leave is here, I don't know what to do with myself!) I'd say generally over a week I had 10 hours of teaching towards it and then probably the same again or a bit less doing homework, so probably 18-20 hours (a week). I did do 15 modules though instead of the usual 12, so it may be less for you. Do you know which exam board you'll be doing?