Air in system

My new central heating system is causing me concern.
A brief description- From the boiler (Glowworm Space Saver - to be replaced hopefully next year when funds allow) the main feed pipe rises vertically to a tee in airing cupboard above hot water cylinder. From tee vent pipe rises vertically and main feed pipe runs horizontally to next tee (100mm distance) where cold feed from F&E tank joins from above. Feed continues horizontally about 200mm then drops vertically to pump (Pegler Terrier pointing correctly down as arrow on body). It continues down to the bypass tee off then on down to motorised valves (S Plan). All pipework 22mm apart from cold feed 15mm.
Since filling there has been a lot of air noise through pump and around feed & vent pipes.
I ran it cold for one evening and noise reduced quite a bit.
I've now run it at full temperature for two evenigs and still there is a lot of gurgling and noise in pump particularily as it gets hot.
I've bled radiators/pump several times - getting a small amount of air out.
Will it quieten down in time? maybe I'm not giving it long enough or is something wrong?
How long should it take to get all air out?
Should air vent up the vent and F&E pipes or do I need an auto air vent as well? This is the highest point in the system.
Any help/suggestions gratefully received.

New system/changes?
why did you have to refill?
Is it pumping over?

Recently moved in to house.
The old pump gave up and several radiators were on last legs.
I took opportunity to go fully pumped rather than part gravity.
It does not pump over - in fact looking in F&E tank while pipes are gurgling/fizzing downstairs the water in it remains totally static.
I'm thinking that because the vent and F&E pipes join at the highest point the air is getting trapped at that point then dragged on down by the pump rather than moving up the pipes and out of the system. The radiators are all at a lower level.
Therefore would an air vent or auto air vent positioned after the F&E pipe as the pipe turns back downwards to the pump remove the air?
The vent pipe is normally warm to touch and F&E pipe quite hot. If the pump is then turned off then on again, it is accompanied by a lot of whooshing/gurgling and the vent pipe gets hot and F&E pipe cold.
I've checked everything I can and all seems to be correct. The radiators are pretty much air free.
Basically I think the air is just not getting out of the system rather than new air getting in! I thought it would go up the vent pipe/F&E pipe but it seems not.