hi could some1 please tell me. i moved into new house and central heating was service before moving in, got british gas to service my boiler which now know is baxi 401 about 25yrs old. to find out combustion box is corroded and now gas switched off. when i told him it was serviced he told me it should not have passed. i contacted the other service person only to be told he saw corroded combustion box and passed it. is this right. i have also been told will cost more tan boiler worth and need new heating system.