Just wanted to say that my DS has also started waking a lot more during the night as well. And yep it happened at roughly about the same time as yours. Mind you when it first started DS was getting his first teeth (and has more coming through at the moment). But I think I have also seen a reduction in the amount of milk he has during the day.

Sorry, I'm not much help, I'm really not sure what to do about it either. I try getting him to have more during the day, but he just refuses... I guess I'm just hoping it is a phase that will pass soon.