Hi there
I spent 8 or 10 nights over the last winter carp fishing at night, but sleeping in my hammock... temps down to -6°C. Never once got cold.
Set up was a DD Travel Hammock, Snugpak underblanket, Army arctic down sleeping bag (centre zip, used upside down as a top quilt.)
I always sleep dressed, in layered clothing. (Long sleeve 'Hottogs' top, micro fleece, and Trakker pile smock top...Craghopper winter trousers and thick wool mix socks. A fleece hat completes the garments for a toasty night.) The bags and quilt just act as extra layers. You can feel the space inside warming up.
As an aside, I'm extremely impressed with how warm the Snugpak underblanket has kept me. I've enven slept out to below freezing with just a light Highlander Ranger 3 season bag, and not felt at all cold. With the shock chord drawn tightly, the quilt is almost like a cocoon, and really does keep you warm.
anyway I was warmer this way than in a bedchair with my traditional sleeping bag.
cheers
Gareth