[Carth]

I'm old enough (as are probably a few here) to remember the power cuts of the 70's. They weren't a massive problem, they didn't last long enough to turn into one.
Back then though, before the great technology explosion (lol) the majority of people/families had a larder stocked with basic foodstuff essentials - no fridge required. The majority also had coal fires and a coal bunker usually kept at least half full of coal/coke/logs. That coal fire (sometimes in more than one room) could provide heat and light, and also hot water if there was a back boiler. If things got too 'bad', with some ingenuity you could also use it to cook some foodstuff and boil water for hot drinks.

All that is now lost to history, and if electricity and/or gas was to be cut off for 3 or 4 days there would be huge problems. IMO the Government are simply trying to prepare and educate people for such an event.