As some other posters have mentioned:
Warm clothing: minimum three layers (vest or tee-shirt, thin sweatshirt, thicker top) especially woollen jumpers, leggings under jeans, sweatpants or long skirt, throws, etc. Consider a hat indoors, and fingerless gloves. Make sure your ankles are warm, e.g. with slippers like ugg boots that come over the ankles.
Move around frequently. Do a bit of vigorous vacuuming or cleaning.
Warm drinks and hot food, even if it is only soup.
Prevent draughts, e.g. towel along the bottom of the door, curtains shut in all rooms except the room you are using during the day.
Get a de-humidifier. Damp cold air is vastly worse than dry cold air. Damp will ruin your clothes and soft furnishings and make the house smell. Keep steam out of your house, e.g. open window and shut door in the bathroom and kitchen when steamy. Dry clothes outdoors. Ensure clothes are bone-dry before putting away (an old-fashioned airing cupboard above a hot water tank is brilliant, or find another solution to get clothes bone-dry).
Get a small heater that gives instant heat, e.g. blows hot air. Use it when you get out of bed whilst getting dressed. Don't have it on for hours as that will cost a lot.