The bleach thing btw is from a little pocket "zombie apocalypse survival guide" I have
. Quite handy really, it has actual tips for genuine societal collapse. A couple of big bottles of household bleach will give you at least drinkable water for decades because you only need a tiny amount. Assuming you have access to a relatively-clean fresh water source (which everyone in the UK does within like an hour or so walk from any location).
Also tells you how to make fires with no pre made ignition source / only wet wood available, etc
.