CH getting too hot - advice

[Spleurker]

Hi,
I have a Sime Halstead Trio Combi.
There is an intermittent fault causing the burner to keep firing on the central heating, which makes everywhere too hot.
There is no room thermostat, just the temp control knob on the front of the boiler panel.
Any advice as to curing this would be appreciated.
Cheers

 

[Kingsway]

you need a room stat to shut boiler down once house is up to temp

 

[kevplumb]

he needs the boiler repairing