There's been a few water supply problems across the country already this winter. Seen at least one thread about it where an op with vulnerable family members was struggling.
My view is that if you don't have vulnerable family members AND you have a bit of space to collect and/or store water, you should reasonably expect to look after yourself for 24/48 hours so that the authorities can provide prompt and consistent support for those who need it. And then get support in place for everyone who needs it (but not as urgently).
What do I do? I have a few cheapo six packs of 2 litre water bottles from Aldi. First hint of water problems I'd fill the bath - not always possible so use pans. A few packs of baby wipes for "washing". Plans for grey water collection to use for flushing the loo. A rainwater butt outside which, if necessary, could be filtered and boiled for drinking, but better for sanitation. I have a lifestraw too but that's only for extreme situations.
I've lived in situations where water was regularly cut off. Most I managed to get was 3 uses out of 1 pan of water - it was a bit grim but I was living alone. 1. Boil veggies/pasta 2. Wash myself (inc teeth brush) or clothes 3. Use for flushing loo. I'd probably stick to 2 uses now. 
Again, I have every sympathy for anyone with small children, elderly or disabled family members and limited space and resources. This thread is for people who don't need to be at the front of the queue.
So what are your plans?