I have a gas fire at work controlled by an external panel with a timer and a
thermostat, it is on a standard plug.

Occasionally the fire will not turn on or gets stuck on and becomes OK again
if I switch the plug off and back on.

I believe this could be down to the other equipment on the ring main, much
of it has thermostats and relays, is this correct.

Do need some sort of suppression? There is none apparent. The place I bought
the heater from suggested one of those metal ring things with the wire into
the panel wrapped around it a couple of times, does this sound right?

It has anti frost protection but as it is I daren't leave it powered as I
often get there on a Monday morning and the place is like a frigging sauna
because it is stuck on.

Any input appreciated.