I have a Brittony II wall mounted boiler for the hot water in my house. This was working fine until recently - now when a tap is turned on the water is either still cold or luke warm or sometimes hot. It often takes a number of attempts to get hot water. When I look at the flames through the view port on the boiler often the flames are roaring away yet still no hot water. I'm keen to have some idea of the problem before getting in a plumber so i can at least have some level of conversation with them. Any info greatfully received.