Hi Paul,
Science In Sport (SiS) do a powdered creatine supplement called KR10 that you can buy off the web (http://www.scienceinsport.com/) and looking on their site that costs between £6 and £20 depending on the size of tub you buy.
I've no idea whether or not it works but I've used their other products - energy drinks and gels - and they seem pretty good.
If you have a search on somewhere like Yahoo! throws up a lot of creatine-related sites. One of them is http://www.absolute-creatine.com/ which seems to have a lot of info.
Dave