how can i fix halstead finest gold boiler?

my halstead finest gold boiler remains on all the time even when room state is turned off , when turned off at power point then switched on seems to work then reignites after a few seconds putting heating on and hot water . changing the clock switch to all three settings makes no difference . how it all started was overnight it was turned off but it started all on its own , turning heating on , there is a clcking noise at start could it be the relay switch on circuit board , only mentioned this because mate looked at it and said , thanks for any possible help