been using the boiler/CH for about a week now off an on, just flushing out any gremlins before the cold weather arrives. have an odd problem with the boiler on start up....when i switch the CH controls on the boiler fires up immediately, runs for about 5 minutes gets up about 50 deg then stops..then it sits there for about 40 minutes when it fires up again and works perfectly until its switched off. same routine every time, have made no changes to the system since last year and the boiler has been serviced earlier this month