This was my sleeping pattern under blankets and a 4.5 tog synthetic duvet during the winter : boil to death for most of the night, then wake up at around 5am freezing cold and have to get out of bed to warm up my wheatie. Then I bought a 405gm wool duvet from baavet, from the bargain box, and my new sleeping pattern is:go to sleep warm and snuggly and stay that way all night!
I do still overheat a bit in the mornings when it's a milder night, but I bought myself another wool duvet (250gm, not from baavet unfortunately because they don't do a thinner weight) which keeps me amazingly warm even in winter.
The other thing I've noticed is that I don't get so stuffed up and snuffly during the night, which I assume means I have a dust mite allergy but never knew it! I'll be buying a mattress topper next, and my mother has bought a duvet and we're both going for the pillows as well when we can afford it! I can't praise the quality of the duvets highly enough.