no hot water

[mark1978]

i go to put the hot water tap on and after about 10 seconds the pilot light goes off on my worcester240 combi boiler and cold water starts to come out, then the boiler starts to make a few noises and suddenly stops then i'm able to press the reset button and the pilot light lights up again but the same thing happens again. I have to also press the reset button about 3 times a day because the radiators go cold aswell would this be a problem with the overheat thermastat. could somebody please help me thanks mark.