heating not working. glowworm 18hxi?

two of my radiators have not been heating up, yeaterday i switched the rest of my radiators off bar one to see if this would push water through the system, the two radiators did heat up for a while but now none of my raditors are working or hot water. i am getting no fault warnings on my display which is showing a green light when firing up, the boiler is firing up the temp gauge is getting up to 64c (even though i set it to max which should be 82c) then shutting off again once temp drops to about 30c then it fires up again, but no heat seems to be getting to radiators supply pipes to some are hot but water seems to be going no further. i tried red switch but it wouldnt push down so i am assuming it has not tripped...help