I swear by using a duvet. Never saw the appeal of multiple blankets. On really cold nights we have an electric under-thingie heater. (Can't think of the official name!) It lives under the fitted sheet. I never saw the appeal of electric blankets: they replace what you are using and already like, and get too hot where they are doubled over. They also can shift around. The one you put under the fitted sheet has none of these drawbacks.