If you're concerned that you and your family are sending gallons of potentially useful water (literally) down the pan, help could be at hand from Hippo the Water Saver; a simple and cheap bit of kit that reduces the amount of water wasted by your loo.
The hippo is made from a squishy plastic composite that opens up "origami style" when placed inside the cistern. It absorbs excess water, and When the toilet is flushed, the water confined within the Hippo is the volume saved. The hippo has a lifetime guarantee, and works with most toilets, saving at least 33% of the water we regularly flush away. A pack of 3 Hippos costs just £7.99 from Hippo the Watersaver
Related: Know your water footprint