can someone help please - i have a baxi 105 he combi boiler fitter, it has worked fine for some 2 years now and is a very good piece of kit. however i recently had it serviced by British Gas and since then it has begun to make loud noises. basically when the heating system kicks in it makes a sound similar to a fog horn on a ship, this is cancelled out when i place the hot water tap on. i have had the gas men out twice since and they have changed a few things but never go rid of the problem. can someone help please, the pressure in the system is fine at between 1 and 1.5. all the radiators are filled correctly and i think no air in the system. hot water is fine and the heating when the noise is cancelled is hot and working. the noise is just horrid evertime the heater comes on it makes it.,..,. thanks mark