I might be thinking of a completely different thing but Seven Trent Water Company (or might be Anglian Water) will post a free water saving kit, in that is a water saving shower head :)
I have used it before as well and it works well if you have poor water pressure, make the flow finer but stronger.
I'm not 100% sure I've given you the right link but I did get my stuff from ST Water. I don't know if you qualify where you live but it's free so why not try?