Fixings! Always have duct tape, nails, screws, garden wire, string, cable ties, elastic bands, etc for repairs, temporary or otherwise.
manual tin opener, maybe two.
Hygiene products for water supply failure. Wet wipes, non rinse hand cleaner, etc.
Generally soap (not liquid), toothpaste, washing powder, washing up liquid, etc.
These disappear fast and disease spreads rapidly when water's off or rationed.
Rubbish bins with lids, for those times when collections are disrupted.
In the event of a prolonged power outage affecting sewage pumping, consider that you might need to bag up and bin human waste until disposal arrangements are in place. Massive sanitary and vermin implications, unless you have good lids!
We've all got candles, torches, stoves, etc but for safety, get some fire extinguishers, fire blankets, battery smoke alarms and battery carbon monoxide alarms. I bought some oil lamps and purchased these alongside.
Water stored in the freezer helps keep it cold if the power goes off.
Freeze a small cup of water and place a coin on top. This is an indicator to tell you if there has been a thaw and re freeze.
You can get huge water bladders to fill the bath with drinking water, if we get notice of supply interruption.