All good advice
Interesting thread. Mine would be keep warm, hydrated and well fed. These three factors effect how the mind works. Its a catch 22 aswell as when your stressed about getting to a border the last thing you want to do is stop and eat, but the lack of sugar in your blood will only make you more weak.
As regards safe water there are a few steps you can follow when in doubt. When taking water from a 'cleanish' stream (the ones you might find in the Scottish Highlands and not central manchester!) walk 100m upstream and make sure there isnt and dead animals/waste up there. Boil and leave to simmer three minutes, maybe even filter it through char that you get from a campfire. You can also use plastic bags to trap moisture from tree branches and metal surfaces to collect dew as it forms in the night.
If in town buy a bottle from a well known brand, or use clorine or iodine.
I feel like a know it all a**e now.