I have a Crosswater Metro shower/bath valve and water no longer gets hot. Crosswater advised me to remove and clean the cartridge but I haven't managed to reach it yet! I've removed the outer chrome casing ok and am left with the 3 protrooding chrome cylinders, for shower, bath and one for temperature control. Each of these has a sort of very small screw-head at the front. I've tried to unscrew this from the temperature control cylinder, using screwdrivers and allen keys, without success.The screw head seems to be damaged. Now I'm wondering if this does screw out at all ....the instructions just say to remove the chrome housing of the controls. Can anyone advise on this? Thanks for any help you can give.