I know there was a post about this some time ago but I installed the water saver thingy about 6 months ago to our shower. If I remember rightly our flow rate was 15l/min and this reduced it to 8l/min. I also taught the kids and the gf that they don't need to have the cold tap on FULL whilst they brush their teeth!
Well after 6 months of using it by DD for our water supply (I'm on a meter as well) has gone from £51 per month to £35! thats an annual saving of £192
Don't sound that much for something that free and saves you money thought it was worth mentioning again and may help offset the stupid petrol increases
Here is the site for those of you that missed it