My dd is now 9 months old and has never been a good sleeper, to put it mildly. Lately she's been waking up every hour during the night, which is hard work.
However, a few days ago we transferred her to a 2.5 tog grobag instead of 1 tog, and it's making quite a difference - she still wakes, but less frequently, and settles back to sleep v quickly. As I'm sure you know, any improvement in sleep makes a big difference - we are having happier nights and days.
Her room isn't cold so this hadn't occurred to me before, but she does seem to like being a bit warmer. Thought I'd mention this in case it helps anyone else in the same boat. (Disclaimer - see grobag website for info on appropriate clothing/room temp/tog values etc )