Hi I am having trouble with running a constant and even temperature from my bath taps. We have mixer taps (not that I think these are at fault). When running the water from the shower head (don't have separate shower, just hose connected to taps), the temperature is ok, then suddenly it goes scolding hot, then cool, then hot, then cold etc etc........ Is it anything to do with the boiler, the taps, or is it the valve (brass inner that has washer on that fits into tap)? Just can't get an even flow of temperature. When my wife washes her hair, she is fine for a while, then yelps out as it is much too hot, then shouts again as it is too cold, and so on....... What is the problem please?