"Last night was -2'c in London with a Northerly wind, and yet all of my windows were left open and I slept soundly." Do you use blankets/a duvet? Have you a t

"Last night was -2'c in London with a Northerly wind, and yet all of my windows were left open and I slept soundly." Do you use blankets/a duvet? Have you a thermometer to monitor internal temperature in your sleeping space? OA recommends 12 to 16 Celsius? I grew up in a (sound, dry) house without central heating in the Northern UK and remember Jack Frost on the windows by the way.