I have just installed one of these: " DiSmart 28mm Swiveling Deaerator"
It works utterly brilliantly. It removed all the air from the system over a period of a few days.
Looks good!
I fitted a SpiroVent about 10 years ago due to airlocks on transitional gas system with header tank and lots of long horizontal pipes in loft. Not had any issues since. (Fited as close as possible to boiler flow.)