I lived for several (depressing) years with no heating in a chilly stone cottage with flagstone floors and no fireplaces. I did the following:
Go somewhere that is warm:
Stay at work/ library/ warm (and free) public spaces for as long as possible.
Warm yourself:
-Wear really warm footwear, and make sure it is well-insulated from the ground if your floors are cold. Having sheepskin uppers is not sufficient if the soles aren't thick.
-Layers. I have Lidl/Aldi merino base layers. Layer up, using lots of thin layers. I found a fleece gilet was good and not too bulky. (I cut the sleeves of an old fleece). And leg warmers. Our local Oxfam always seems to have loads of base layer kit. Wear the right type of clothes - wool, fleece, etc. Cotton isn't very warm.
-I used to snuggle up on the sofa in a sleeping bag with a hot water bottle (or two) in it. Now I have an electric throw, which can be used when I'm sitting or on the bed.
-Have plenty of hot drinks/hot food. I use insulated cups/ flasks for a ready supply.
-Make sure there are layers on your bed. I used to sleep in a sleeping bag. Make sure there are layers under you as well as on top. In the middle of one very cold winter, I made a small tent-type construction over my bed, like having a four-poster.
-Exercise! Dancing is great.
-Wear a hat and a buff. And gloves/long sleeves. A fleece with a hood is great, as it reduced draughts.
Warm the space you are in:
DO NOT RELY ON CANDLES! They are rubbish for heating, and those candle pot heaters you see on the internet defy the laws of physics. They are also a terrible fire risk, and make your house sooty.
Rely on the oven/shower steam, etc for heating ONLY if you can make sure it's not causing damp. And don't dry your clothes indoors. If the cost of fuel is worrying you, you don't want to add to that with the cost of dealing with mould.
-People give off heat. Have friends over. Tell them to wrap up warm!
-Block off anywhere that isn't used and don't heat it unless there is a risk of damp
-Keep the curtains open when there is sun, and close them as soon as there isn't.
If you have paid for the heat, make sure it stays inside.
-Thick curtains. I used to safety pin cheap Ikea blankets in as additional liners. I bought velvet curtains from charity shops.
-Bubble wrap on windows. I taped it on with double sided sticky tape. And on metal windows, make sure you cover the frame of them too.
-Bathroom windows: I use shower curtains over the bubble wrap to let the light in but keep the additional barrier.
-Plug up your gaps. Especially around windows. Don't seal ventilation brick, though - they are there for a reason.
-Rugs. Make sure there are no draughts from under your floors. consider insulating under your floorboards (we used Celotex in the current house)
-Use draught excluders on the gaps under doors.
-Make sure your doors/windows have insulation strip around them.
-Put a cover over your keyhole and letter box.
-Block off unused fireplaces/ spaces where air can escape. Even if it's just with a chimney balloon, or cardboard taped over the front.
If it is dry and cold outside, wrap up and go for a walk. It makes inside feel warmer by comparison.
These days I have central heating, which still feels like a miracle. I have a really good timer so I can choose when it comes on and at what temperature. I also have a log burner, with a fan on top, and a metal kettle that can keep me topped up with hot coffee when it's on. I've also cooked dinner on it.
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