Central Heating,strange customer.Normal day,get to my third promised am. call to service a worcester boiler.As normal,I always ask ,;Is the boiler giving satisfactory performance,any problems with heating or hot water?No, says thje customer,everything working fine,just a service.[Boiler has not been looked at in seven years!]Anyway carries on with normal service procedure,boiler ok, gas rate ok, emissions within manufacturers recommendations,etc.Completes service and fires system for further checks.Discovers that the zone valve fo the c/h is not operating on demand.Further investigation shows zone valve to be leaking water thro stem and inoperative!Explain to customer that the heating side of systen will not operate for aforementioed reason,and then gave a price to correct this problem.he replies, too expensive,I will carry out the job myself,O.K. says I and off to my next job.Two days later his wife rings the office,nothing working,since boiler service[in the meantime husband has drained system and attempted to renew heating zone valve on s plan system]Result ,incorrectly wired valve, blew p.c.b. on boiler board.fired boiler with no water in system,tripped on overheat,cold water entered boiler in overheat condition and cracked ht. ex. on boiler!Can you now come and fix the problems my husband has caused?Yes we can, but it will cost considerabley than the original estimate for renewal of motorised valve.Husband:s occupation,saxophone player,I myself cannot whistle in tune.Ithink that he has a better job than mine.