Usually I don't allow it, but in the cold it's Lovely to curl up on the sofa with the throw draped over us and our 2 dogs curled up either side, they keep us nice and warm.
Our heating is used sparingly, in order to keep the warmth our loft is well lagged (we're in a bungalow) and doors (internal and external) should remain closed to prevent the heat from escaping, using those snake things along the bottom or a heavy curtain to prevent drafts.
When cooking a meal, turn the oven off about 5 minutes before the cooking is done and allow the heat in the oven to finish off the cooking on its own. Once all food has been removed from the oven, leave the door open to allow all that heat to escape into the kitchen and warm that room up too.
Nothing beats a warm cup of tea or coffee in the morning to wake you up and warm you, but instead of "boiling just enough water" fill the kettle right up, once the drink has been made pour the rest of the hot water into a thermos flask which should keep it warm throughout the day for each time you need another cup.
The sun can still be warm in winter, so be sure to keep those curtains open for as long as possible to trap the heat of the sun inside, also invest in heavy curtains which, when closed, protect from draughts
Above all, the best tip is to visit a friend, relative or neighbour. time it right and you may even get a meal out of the visit too, alternate between friends so that no-one gets suspicious, or just agree to take it in turns, costs the same to warm a house for 2 people as it does for 4, the tv is being watched anyway and it'll costs hardly any extra to cook for 2 more people