For May bank holiday weekend, I put a foil-backed picnic rug as the base to my sleeping space, then a blanket folded in 2, then my SIM, 4 season sleeping bag, and another fleecy rug/blanket doubled over on top. (I am a cold creature and wanted to capture as much sleep as possible between Cub middle of the night emergencies - next Leader we allow in will be a second woman!!). I also use a hot water bottle and thick dry socks (a pair kept for bed).
Once dinner was over and washup done, I changed for bed, sort of. I changed my under-layers, put on thermals (long legs, long arms ones), added my comfy jersey PJs, then put my fleece lined trousers and Scout jumper back on top, for around the campfire etc. At that stage, I also put on a woolly hat.
When it got to bedtime later, I took off the outer layer which was a little damp (misty evenings), but only had to let cold air at my feet as I changed socks - I put a dry hoodie over the top of my pjs but didn't have to change those layers, put my hat back on and hopped into the bag. It's much easier to keep the air trapped in your layers close to your skin warm by not moving them too much than try to get warm again late in the evening.
I have always tended to sleep with a hat on and a thermal layer when camping (never get lucky enough to get really warm nights!). But insulating UNDER your sleeping bag is almost more important than extra layers on top, as the cold tends to come more from the ground than the air.
And of course, a hot chocolate just before bed is very useful too. (Alcohol isn't great anyway but totally not allowed on Scout events so wasn't an option). I also bring a flask of tea to my tent - with the milk in, ready to drink, in case I have to get up later and need something warm to settle me back (in case - see note above about the next Leader!! Apparently Mammy's are what's needed middle of the night) and again for my first thing in the morning cup, before facing Cubs and demands for breakfast while still bleary eyed....