From your information the 280h would suggest it has an atmospheric flue? If this is the case it would be one of the range that uses a servo-valve to change the position of the diverter valve.
It is probable( if i'm assuming right) that the servo-valve is sticking in the hot water position.
To test, there should be cover over the control section at the bottom of the boiler held on by a screw at either end. Remove the cover and locate the servo, centre of the boiler at the bottom, with several small pipes coming out of it. Carefully check it while getting someone to turn a hot tap on and off.
You should see a lever at the back rise and fall in an arc. When the hot tap is turned off the mechanism should be pulled down to the right. Some times they stick and don't go far enough down to the rest position. Gently (very) press down the lever where the spring attaches on the back. That should let the heating come back on until the next time the hot tap is operated.
If this works you may need a new servo or some work on the feed pipes or d/valve.
Try it and see... Then again i could be totally wrong..hope not.
T.H.S, May 2007
