There are plenty of ways to save water, control valves, water at the correct flow for your speed ect. And when all your work is established as wfp you will use much less as well. If you have a good ro £100 is about right for a one man band.
As far as using a merlin on a water meter, that's almost like burning money. Invest in a 4040 and you'll be quits in in just a few months.
Simon.