All water companies offer this aid. FYI dual flush toilets don't need save a flush bags as they can flush a full of half cistern of water. If you are with Anglian you need anything you can get to reduce your bills !!! Expensive !
Government legislation stipulates they have to spend a certain amount on helping people reduce their usage, this is the cheapest way for them. Similar to the free lightbulbs the energy companies used to give out, the cheapest way of meeting a government policy imposed on them.
It's not free really is it. These are a gimmick and Anglian know this. You pay for it through your bills, why don't they just tell people to put a weighted object into their cisterns. Anyway some toilets with duel flush cannot have these placed inside!
Fab! a plastic milk containers - filled with cistern tank water - works too