Hi Barry, 

Hopefully you're employing the services of a mechanic now. Without the model year or engine we can't look for common issues, I'm afraid. Perhaps there's something up with the radiator itself, or blocked coolant channels after the head gasket was replaced. Something electronic could be causing the engine to run hot without cooling as well of course. 

Lastly, is the engine actually overheating or is it just the coolant gauge that's appearing to be too high? If it's the latter, perhaps there's something up with the temperature sensor.