Yes the valve is easily replaced,turn the water off prise up the white grommet that is in the top of the valve with long nose pliers if possible,remove the silver screw at the top back of valve,then prise up the valve,it is in a keyhole type slot so it will pull forward once prised up.Fitting is just the reverse not forgetting to refit the grommet with the capillary pipe.A spare valve can be obtained from National shower spares
toptrish, January 2015