Pontius,
you are bang on ref the water. My brother worked at MOD and it was tacitly aknowledged there that all the cunning survival plans would founder on the lack of uncontaminated drinking water. Also there was a 'worst estimate' of how many servicemen would actually leave their families 'in the lurch' if the balloon went up for real. As for the guards on the gate keeping the families off the camp as they tried to gain access to our supposedly superior shelters, it was also accepted that this would not be the case.