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Thanx Butler 020. There is no problem with lighting the flame head initially with the ignitor which happens immediately.
The flame control knob has to be pressed in to allow the gas to flow to the head for initial ignition.
No problem until the knob is released in order to turn it to the full flame position and the gas cuts off.
I have cleaned as much as I can see.
There is a thermo couple sensor at the flame head which I assume should send a signal to the valve arrangement to allow the gas flow valve to remain open to supply the full flow.
Perhaps this is the faulty bit.
I can not find So'Lar as a company anywhere on the web so stuck insofar as to consulting the company.
Thanx anyway for your interest and suggestions.