apologizes Agile, when i originally posted a search ( before becoming a member)for flash green power light on halstead boiler this link came at the top. Someone else may have the same problem as myself and could save them some hassle even though the link is old its not out of date its hard work...
i have just encounted this problem checked flow switch, flame probe etc
lastly i checked pump this had stopped rotating and is the route of my problem hope this may help someone in the future