I changed over to a water meter and now pay less than a third of what I used to do ! Mind, there is only one of me here (plus two felines who don't really do showers....lol). You can go for a water meter and change back to unmetered water if you let the company know within a certain period of time (I think it's something like 12 months but don't quote me on that). If you go on line to this site, it will be able to check for you whether you will actually save money or not.
http://www.uswitch.com/Water/Why-Switch.html
I did this and it appeared I would save at least half of what I was currently paying. I then applied for a water meter and went through some similar checks with a lovely lady from my local water company who confirmed that I should save at least half what I was currently paying - as it turns out I now actually save two thirds, so I am a very happy water meter user !
They fitted the meter just above the stop valve in the street so no internal alterations were required. A totally painless way to save money.