I have had a light box for years and yes they do help.
ideally you should start using them now
I have a large box one which my husband turns on when he leaves for work at 4.30 when you waken the whole room is bathed in would be sunlight........worse month for me is december once over that heyho spring is on its way! good luck
I considered getting one a number of years ago when I lived in Bedfordshire......then I moved down to Devon and the difference in number of hours of daily light seemed to make an appreciable difference. Before that I would start dragging myself in October until I started to feel 'buzzy' again in Feb/march. But as chrissy says,December is still rather awful.