This is more for the future because it requires some initial outlay.
Blankets and hot water bottle when you're sat on the sofa. Cheapest is to find a pile of second hand blankets on Facebook from someone who's had a clear out. Check the size before agreeing price in case they're tiny baby blankets.
Hoodies and a scarf makes a lot of difference to being warm, humans lose a lot of heat through their heads. Outgrown jumpers make good woolly vests if you cut the sleeves off and cut a slit to make a V at the front so their head fits through easier. Looks rubbish but you can't see with another jumper on top. Long sleeve shirt or t-shirt under jumper as well as vest. If you have tights or leggings wear them under trousers or jeans for an extra layer. Thin socks topped with thick socks, then slippers or keep your trainers on if no slippers.
Sleep in your bathrobe with the hood up as well as pyjamas and socks if it's freezing. Add your hot water bottle and the blankets from the sofa.
Rice pudding (amount per person): half cup rice, one cup milk, two cups water. Bring to the boil in a saucepan, then simmer while constantly stirring, keep tasting and when the rice is soft, drain off water and serve, with a teaspoon of sugar and a big spoonful of jam mixed in per person. Fills you up for ages and is a sweet treat for DC.
Porridge is filling too, the own brand bags of it at the supermarket are cheapest, half cup each of porridge, water and milk, microwave for a couple minutes.
Massive box of eggs, they'll keep at least 3 weeks in the fridge and a few days after they've been cooked too. Boil them on the job or poach them in the microwave (bowl of water, crack open an egg, 6min on half power) or make scrambled egg on toast.
Pasta (can be done in the microwave, half power 8min) with cheese, tinned tomatoes, vegetables, tomato soup (as a sauce) all mixed in with pepper to season.
Banana is filling.
Bread with jam.
Tins of soup with bread.
Own brand digestive biscuits.
Own brand squash juice, cup of water, microwave 1 1/2 mins to save boiling the kettle.
Casserole: water, any vegetables and meat, stock cube, bones (remove before eating), pearl barley (near the pasta etc in the shop), dollop of Bovril, boil then simmer (or oven) until hot and cooked/soft.
Spaghetti mixed with baked beans.
Beans on toast.
Cheese and tomato sandwiches.
If you run out of washing powder put whatever you've got in the machine. A squirt of washing up liquid, shampoo or floor cleaner will work just as well.
Flour and water mixed into a paste for glue and rip up magazines to make paper chains to decorate the room. Use clothes pegs to hold the loops together until dry.
Visit the library, it's warm, dry and free.