I agree with PP that they seem to just pluck a price out of the air for every house.
We're unmetered, so we pay based on the rateable value, as does my MIL. Similar-sized houses on comparable roads, three minutes apart. Her bill is slightly over double what ours is?!?!?!
I know the 'received wisdom' is to get a meter, but even from this thread, it sounds like the charges are quite random, whether you have a meter or not.
My concerns about getting a meter are twofold. Firstly, if a hidden leak sprang within our perimeter, we could end up paying an absolute fortune; and what incentive would there be to the water company to fix it?!
Secondly, call me a conspiracy theorist, but I wonder more about what could happen in the near future rather than necessarily how it is right now. Once everybody is on a meter - either forced or encouraged by talk of big savings - there's absolutely no reason for the sayer companies not to ramp the prices right up.
Think how much more efficient ICE car engines are now than 20 years ago, and how much less fuel they use overall. It should be loads cheaper to buy the fuel now than it was then; but it isn't! Millions of people were encouraged to invest in electric cars - partly based on the promise of zero-rated VED to offset the higher purchase costs. That's now been scrapped.
Companies seem to start with an idea of the highest amount of money that they can get from consumers, and then work backwards in their pricing per unit calculations to make sure that people end up paying that amount regardless - all the while being nagged to use less and less, but still with ever increasing bills.