Done a bit of camping in my time and the only way i can normally stay warmer is by having someone over the out side of my bag ie like a rug or my jacket.

If i sleep in a sleeping bag thats big and clumpy i sweat on the underside and get chilly on the top side because of the sweat.

Another best way to stay warm is a simple large set of dry socks, set of long johns (or similar) and a thin long sleeve t shirt

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Plough on