Which? trusted traders is an endorsement scheme that recognises reputable traders in the home improvement and motor industries. Also earn tesco clubcard points as you pay your boiler services bill for every €2 you pay off your boiler services bill, you get 1 tesco clubcard point.**. Book direct, 24/7, 365 days a year. New setups by certified technicians don’t void the warranty of the appliances for instance, a manufacturer of water-heater mandates.