Actually the shortage of pain killers has more to do with illegal drugs trade than Brexit.
And all panic buying does is encourage otherwise normal people to panic buy
As to power outages etc, that's purely weather related and hardly a new concept. Getting a couple of days worth of extra stuff in is common sense if you might not be able to get out for a bit.
We have about 15 litres of bottled water for drinking and about 400 litres in water butts for flushing purposes. There's always a few tins of soup etc in the cupboard anyway. If we lose power then we'll lose heat and light... nothing that bed and torches/candles can't overcome. But still have gas for cooking.
In twenty years we have probably had less than a week in total hours without electricity, and possibly ten days without water. Never has the gas been off.
Currently on a shake based diet, so as long as I have water, or access to it, I have enough food to last until mid March.
So, in the immortal words of Catherine Tate, Face? Bovvered?