If the situation lasts beyond a few hours, three things determine how bearable it is, and they are not the three people expect.
Water first. A person can go a long time without food and not long without water. Fill containers, the bath and every bottle in the house the moment you think supply may be interrupted — while there is still pressure in the pipe. Water in the system is not yours until it is in a container.
Light second. Not for comfort: for not falling down stairs, not standing on broken glass, and being able to see what you are doing at three in the morning. A torch and spare batteries beat a phone, which you need for other things.
Warmth third. Heat is lost through the walls and the windows, not the ceiling. One room, door closed, everybody in it, is warmer than a whole flat at the same cost. Blankets and layers work; a fuel-burning heater in a sealed room kills people every winter.
Never burn fuel indoors without ventilation. Charcoal, petrol generators, camping stoves and unvented gas heaters produce carbon monoxide, which has no smell and gives no warning. This is the single most common way a survivable power cut becomes a fatal one.