HELP, came home from work last tuesday to find pilot light on my old baxi back boiler had gone out, got CORGI reg. lad out to it next day who gave it a "FULL" service. ( i think the boiler is older than him,do newly accredited persons train on these old jobs?), he was nice enough though he explained that although the actual burner was v. clean the heat exchangers were clogged with too much carbon for it to be working properly,he then proceeded to clean them up. conclusion being that the fire/chimney was not drawing fumes up, said i needed a vent in front room,flue cleanig/repair and a new cowl on chimney,* honest answers now *a)how much would this work be? or b) am i throwing good money away having this work done or should i bite the bullet and go for a combi.