worcester 230 pilot light lights but nothing else?

i have a worcester bosch 230 rsf combi boiler. when a demand is created (ch or hw) pilot light ignites and stays lit but main gas valve doesnt open. the fan is turning o.k, the overtemp thermocouple is working fine and the airflow pressure switch is operating. any suggestions? ps just for now i have linked the pilot light live and the main gas valve live together as this gives me heating and water for now(but dont know at wat cost. any suggestions would be appreciated - rickey