I pay only £18/month for my water services on average, as a single person living in a house. I do wonder if many of these water saving devices are really cost efficient when the cost of water is so low. I think the biggest usage of water is the Bath/shower so that is impossible to reduce, the toilet is the only thing which could be reduced, but sometimes if the water level is too low you need multiple flushes eliminating the benefit entirely. A water butt is the only thing I can think of that saves a serious amount of water, but even then the initial costs are quite expensive.
I am not aware of those water saving devices or any other, what I do to save water or electricity is to close my lights and other devices when I am not using them. You can also use a device to cut totally the electricity so that the presence lights don't stay on, as well as replace the old bulbs by the efficient "new" ones if you haven't done that yet.
Water saving toilets are a waste. They usually take 2 flushes to rid you of the waste. If you have the space outside get a water catchment system and start using that for flushing your toilet. Boil the catched water for drinking and brushing your teeth. It requires some work but it will save money.
