I have an ancient Concord WRS 240 boiler which has decided to stop providing me with hot water/heat. I have proved the mains supply to the back of the thermostat control box, and also proved the 240 output from that to the gas valve. The pilot light is on ok. From this I'm thinking the gas valve must have packed in, or the pilot light sensor. I'm going to get a bloke in to fix it but just wanted to know what sort of cost a new valve is likely to be just incase the chaps pen slips by accident when he's writing his quote. The boiler is at probably about 20-25 years old by now. Its a bog standard gravity fed system.