I used to camp and go to festivals so I have a little solar radio that also functions as a torch. It works well. And a ‘wind up’ torch that you pump a button on (rather than actually wind) to charge it. We also have a solar charger for phones. We have sleeping bags in the attic but plenty of blankets in the house if needed anyway. We do have a toddler so obviously if the power went out, his monitor wouldn’t work, but we’d probably bring him in with us anyway for warmth.
We have had central heating, but also have one electric radiator at the awkward end of the living room. And our hob is gas but the oven is electric. So if one or the other goes out, we should still have a heat and cooking source (with matches or a lighter to light the hob, as obviously the ignition switch is electric).
We always keep our cupboards well stocked anyway. We could manage a few days no problem.
For people worrying about cooking food but not wanting to spend money on a camping stove or similar that they’ll likely never use outside of an emergency, what about a BBQ? It’s something most people have. Even getting a few disposable ones, so you could eat one hot meal a day, would be useful.
Otherwise, cupboard food that stores well and doesn’t need to be heated to eat is fine. Crackers and crisp breads can be used instead of sandwiches, with something like peanut butter. You can get jars of pickled beetroot, peppers in oil, tins of fish/meat etc. Even beans can be eaten cold. Many soups etc can be too; just check the labels.
Don’t forget that a lot of things need to be refrigerated once opened, like UHT milk. So if there’s no power, and you use a bit of milk for cereal and a cuppa, you’d have no way to store the rest of the carton safely. Better to buy small cartons than big ones, or even buy cereal bars instead that don’t require milk to eat, and powdered milk for drinks.
You don’t really need to buy anything special to be prepared. Just try not to let your cupboards run low, and make sure you have some painkillers and basic first aid supplies to hand.
So the only things you might need to buy specially are a torch or lantern, a small radio, and maybe something to cook with (even if it’s a cheap BBQ, like the little ones you can take to the beach etc). And don’t forget batteries!