Ideal ff series boiler?

Hi Guys I am currently having issues with my heating system, where as more boiler fires up no problem but it cuts out before reaching roomstat temperature , if i turn up the stat on the boiler it fires up again but then i find our hot water is far to hot, the stat on the hot water tank is set at 60 degrees and i have changed the thermostat which is on the tank, can anyone please help !!