Most definately working.

Air does tend to also get trapped on pipework around the boiler, since
the feed & return drop down 2m immediately before/after the boiler if
you get my drift, i just bleed these using the manual air vents?

Is it really necessary to have auto air vents wherever air tends to
accumulate to ensure all the air comes out of a sealed system? I sort
of assumed that after a short period it would just end up in the rads
where it can be bled out, leaving an air-free system.

My gut feeling is air is being pulled in around the area of the pump
inlet, is this possible and how common is it?

Thanks,

MH