Pilot light with Lincoln - LGD25/35 warm air central heating boiler?

The pilot light on the boiler has blown out so went to re-light it. Had problems with keeping the pilot light lit so we turned the thermostat up to get the main furnace working. This worked fine and system was lit and going in the morning.

Late on the night noticed pilot had gone out again, I could hear gas and pilot was lighting then going out once button was released. Belive this could be caused by a dodgy Thermocouple?

I have tried to light boiler since but now pilot wont even light and I cannot hear any gas like I could before going to the pilot, even though the gas is on as other appliances use it.Tp
Any advice on what could be the problem?