Dont touch any of the valves under the boiler. The yellow valve under the boiler is the gas inlet, you shouldn't be touching that at all.
What are you calling the stop cock? Have you isolated att cold water supply to the house or are you taking about the black valve under the boiler?
Boiler can be on, but will probably still show you a red light at the moment.
What are you calling the stop cock? Have you isolated att cold water supply to the house or are you taking about the black valve under the boiler?
Boiler can be on, but will probably still show you a red light at the moment.