I have a problem with the temperature dial on my shower. When I turn it, it creaks probably because it's on a nylon spindle and it's quite hard to turn and switch off. I fitted a new one but it's just as bad. Do you know if you can get a new centre spindle for this shower ( Idoubt it) or would it have to be new pump. If so, approx how much would it be and are they easy to fit?