how can i fix my ideal mexico rs 125?

hi there i have an ideal mexico rs 125 all of a sudden i have no heating, the pilot is on in fact i accidently put it out when i touched the gas valve but relit it ok, i then backed the thermostat knob to off and turned it up to 6 the boiler lit up it then went out after a few minutes but pilot is still on,when i pull the capillary thermostat out of the casing the boiler lights up and runs so i think this is ok, i went round bleeding all the rads some had alot of air some did not bleed as should at one point i got some heat but wasunable to keep it going, the thermocouple must be ok as the pilot seems fine the pump is running ,the expantion tank is not frozen has a supply of water is available any ideas.