my glow worm condensing boiler keeps saying overheated?

It might be overheating due to a number of reasons like poor system condition ie sludge or a failing pump etc, or maybe some trapped air, is their water in your system? have a look at your header tank, is the ball valve stuck? If my memory serves me correctly their is a tiny round inset button that you have to hold in with a pin or pencil to reset it on the bottom right of the control panel. If it keeps locking out get someone in as it is overheating for a reason and this will need to be looked at Kind regards Terry

Hi Jeremy, I would check if your pump is running as this would keep overheating the boiler as the water is not being moved around.

you need to get a local engineer to look at it