Boiler not firing up

Hi, I have a fully pumped system with a Potterton Flemingo ll boiler. Pump working, heater and water stats working, valve and valve micro switch working. The Pilot light on the boiler working but the boiler is not firing up. everthing was working early this morning, but could here water glug, gurgling and trickling sounds in the system. The trickling was located to a couple of rads. Bled one of the rads, it was cold, and plenty of air escaped. The rad immediatley warmed up. It was after then that I noticed the heating went cold.
Apart from the boiler not firing the pump started to make a hell of a racket. Replaced it with a newer on. Pump ok, and boiler fired up, then back to pilot light again. Tried to bleed other rads but no air or water escaped on any of upstairs rads. Please someone help!!!!

You clearly have a blocked feed from your F&E tank.

For a temporary cure you may be able to fill it by pouring water down the vent pipe but you will probably have to cut out a section of pipe where the feed joins the flow pipe.

Tony