replacing cartridge from Bristan thermotech shower (Prism)?

I have replaced the cartridge in our bristan shower but there is no cold water flow (only hot) when i turn on the flow control. I have checked that both hot and cold supplies are getting to the shower body (cartridge housing) which they are, so there is obviously something wrong with the way the cartridge is set up. Does anyone know what is causing this?

Paul Enticknap
October 2009