Potterton Netaheat Radiator problem

It'll be an air lock in part(s) of the radiator circuit.

The standard method is to a) Temporarily try a higher pump speed. To get the air shifted into the rads where it can be bled. b) As above but shut down all but one rad at a time to really try to shift the air around.

Note that you could have a near blockage where the make-up water from the F&E tank joins the primary circuit. This means that bleeding is often ineffective. The system used to work so there is every good chance that you'll win eventually.

Ok i've bled all the radiators individually, i noticed if i bleed one for long enough eventually hot water will come through and heat the radiator. Anyway the radiators are still not heating up when the boiler comes on.

Where will I find the pump that pumps this water around (as per point a above)? And is there anything tricky about turning up the speed on it?

Thanks in advance.

Just one further point, I found the pump and it seemed to be on (a hum and slight vibration when i touched it). However it was set to its top speed already 3 and was quite hot (perhaps I should turn this down).

So the Boiler looks to be funcitoning correctly, the pump seems to work and I can bleed the rads until hot water comes through. But they just dont heat up when I turn the boiler on.