i have a problem with heating coming on 1st thing in the morning?

have a puma 80 combi which is about 12yrs old. When we turn the heating on via the room stat in the morning the boiler does not come on for about 30 mins. through out the day the boiler keeps going off even when the wireless stat shows its calling for heat. We have to keep the thermostat switch for c/h on the boiler turn up max. Hot water from the boiler not a problem.