My husband, who is the chilliest mortal in the entire Northern Hemisphere, persuaded me to sleep naked when we were newly married. (Snigger if you must!)
He maintained, quite rightly, as it turned out, that you are much warmer in bed wearing nothing than wrapped up in night-clothes.
It does help if you can afford to warm the bed, either with an electric blanket or with hotties.
Admittedly, we can still afford to have some heating on, but DH, me and two cats in bed - humans under the duvet, felines above it, manage to stay warm all night. Although I do sometimes find my wee black bogle under the quilt that goes over the duvet in the morning.