COL tenants now have to pay their water bills themselves rather than have them included in the rent. If you are a single occupant and can't have or don't want a water meter, Thames Water offer a single occupancy discount. My original bill was over £380 per year and is now £254, that's a third cheaper. That is based on a one bed flat, it might be different for a studio or 2-3 bed, although I can't see how someone on their own would use more water if they had more bedrooms. 

If you know any residents who live on thier own who are not on this site, please let them know about this.