Duvet and blanket combo

In these chilly times it can be difficult keeping warm in bed, especially if you don't have central heating. An efficient and cheap trick I discovered in the last few years is the discovery of the duvet/blanket combo.

What I do is spread an old blanket (probably circa 1950s/1960s) over the top of the duvet so that the blanket drapes over the sides of the bed and duvet. This creates an additional layer, but more importantly helps weigh down the duvet so it doesn't move around so much and helps to fill gaps between the duvet and mattress that may develop when you move around.
Because the blanket is a more flexible material, when the duvet shifts to one side, the blanket fills any gaps that might let cold air in. It is important that the blanket drapes over the sides of the bed.

The result is that I am usually cozy warm in the morning, instead of waking up with a cold back or bum because the duvet is half hanging off the bed!

A really cheap and efficient solution to a modern problem, assuming you can still get your hands on a blanket!