As our house was new when we bought it in 2005, a water meter was compulsory.
I believe that if you don't have a meter, the water is charged in line with what used to be the rateable value of the house.
Some friends moved to a housing association bungalow and were getting large bills, so changed to a meter. Bills much lower now, and as they sometimes go away for 6 weeks at a time they are only paying for water they actually use.
However another friend refuses to go down that route as his house is a fair distance from the main, so there there is quite a bit of pipework that goes across his land. He worries that a leak could develop along the pipeline and that if he was unaware of it he could be charged for the water lost, if you see what I mean?
hilda it could be worth speaking to your local water authority. Ours (South West Water) has a policy whereby you can have a meter fitted for a specified period and if you find you are NOT saving money, it will be removed and you can revert to your current system.