Wall mounted Gloworm gravity feed boiler. I switched off gas to fit a new cooker fixing. No problem there but after switching on gas and attempting to light, the pilot will light while I hold in the button, however as I release after required 30secs it goes out. Don't think I have missed anything (I followed instructions to the word many times) but it has been suggested that a thermocouple fault could be the problem. Sorry do not have boiler number but its one of the small fuel savers approx 14yrs old.