I have the above boiler serviced by BG every year. They say it is an excellent boiler and from the internet there are common parts available. The problem is we use it for an hour in the morning and evening to heat the water in summer. It now starts, goes through the first cycle until the pumped circulated water in the boiler reaches the overheat? thermostat setting and switches the gas off. This takes 5 mins. When the water has cooled it a bit (low boiler thermostat temperature reached??), the pilot lights but the gas valve doesn't open. After a min or so the pilot goes out but the fan continues. It remains like this until the time clock switches it all off. If however at the point where the pilot goes out, or any time after, I restart the boiler either at the programmer or on the boiler switch, it then restarts and goes through another cycle. This can be repeated a few times manually until the hot water tank is full of hot water. The question is what is wrong and can it be repaired easily?