We've had a new Logic plus combi fitted, the hot water is set to 50 degrees but when turned on comes out a lot hotter at around 60 and gradually cools down to the correct setting of 50. I've watched it doing this on the boiler display too. Is that normal because it's worrying that the temperature can vary like that if you're in the shower. I know I can install a TMV but I'd have thought it would be the reverse, i.e. the temperature starts off low and gradually builds up and stays at the setting of 50.