My boiler has started to play up. When the boiler starts up in the morning very often the thermal cutout switch will pop out straight away. When I push the switch back in the boiler fires up and works fine all day. I have heard the water pump make a bit of a noise recently and plan to replace it. Could it be that pump is seizing up a bit while not in use overnight so come the morning the boiler overheats because there is no water circulation?