Cooking:
Do you have a BBQ? If so this is one way of cooking. You could use camping pans to heat stuff up on the BBQ or do jacket spuds wrapped in foil)
If you have a shed for storage then camping gas stove and gas to use outdoors.
Have a small supply of add water foods:mug shots, cup a soup, cous cous. Instant mash, instant custard.
Also a supply of heat up quick foods. (Baked beans, rice pudding, custard tins, curry tins, tinned veg to go with the curry)
Have a flask for any hot water you heat up. Wrap it up in an old coat to keep it hotter longer. (Save going out more than once.)
Also have a food flask.
Lights:head torch, solar lanterns, (one per person) battery fairy lights if you have them already.
Mobile phone: power banks. One per device. Keep charged up. Enough data on your phone for emergencies .
Warmth.
Reusable hand warmers.
Blankets, duvets.
Hat, scarf, snood, wrist warmers, thermal base layers, thermal/wool socks.
If it's fucking freezing and you have no heating you can all gather in one room or even camp indoors.
General house prep:
Well insulated attic. (At least a double layer of insulation)
Lined curtains. Make a massive difference.
Carbon monoxide detector. (You might get neighbours cooking indoors and leaking through to you. )
Smoke alarms.