Like Catherine, I used the ChoiceSwitch site recently when we moved house to work out what company would be better for gas and electricity. They were really helpful. I put in my details and they called me within half an hour. Then once they told me the best deal for me they got my ok to pass my details onto the other company (which happened to be Red Energy) and they also called me back within half an hour. I thought it was great and it doesn't cost a cent

Unfortunately you don't get a choice with water companies though. You just have to go with the water company that deals with the area you live in.