Thanks both of you. As I’m actually located in Spain we follow different rules over here about who can/cannot play with gas (like there are hardly any, apart from the 4-5 yearly gas safety inspection on appliances, and nothing like the hellish rules you have to comply with in UK). Also we don’t have mains gas (it’s all butane/propane bottles) disconnecting is very simple. When I’ve got time I’ll try the clean suggestion, take it apart, clean the gas control parts & see what happens.