Having a meter installed was, it seems likely, a very good idea. Why on earth I hadn't done the maths before is beyond me. At this rate, our annual water bill will be around a quarter of what it was.
@NAB We are having a 'Smart Water Meter' installed at some point (it may have already been done - it'll be in the street apparently).
Severn Trent will give us the opportunity to see the data to see if changing from fixed to metered water will be worthwhile.
To date I've resisted a water meter.
@MikeFromLFE I asked Severn Trent if I could have access to the readings - they said no (but that it would only be summary data for several days/weeks at a time, so not really useful to me anyway). They wanted to put the meter out by the stopcock in the street but I requested that the meter be fitted in our plant room so I could automate reading it myself. They do say that we have the lower of four bills or two years to change our mind, so getting a meter seemed sensible.
@NAB I gather that we are part of a widespread trial - if memory serves correctly it's most of Leicestershire and parts of Shropshire (random - but it's Severn Trent!)