My shower was going cold after about 2 minutes. Did an experiment and discovered the boiler was actually shutting down so that was why. After about a minute it would fire up again and the cycle restarted. Read on various forums that some shower heads will restrict the flow of hot water (cos holes too small) and the boiler, as a safety mechanism, will shut down if the water is not taking away the heat fast enough. Is this right? This is supported by the fact that when I took the head off, the boiler was fine. Does anyone know what kind of shower head I could buy that would prevent this from happening again?