Thanks all, just the living room radiator and pipes leading to it through kitchen mainly. Makes the normal creaking when heating up, but on the cool down for about half hour after heating turned off it's loud clangs. Maybe it is pipes contracting on cool down just seems louder with new boiler, even though the CH temp/pressure is same settings as old boiler. Tried bleeding that radiator but no air coming out at all and heating up evenly anyway.
Also when the CH water reaches its temperature and the burner turns down it makes a noise that can only describe as like an aeroplane passing in the distance, low hum steadily decreasing in frequency for about 10 seconds. Assume this is the fan stopping? Noticed this as soon as the boiler was put in couple months ago but seems to be louder now than it was, can hear it faintly in bedroom when heating on first thing in the morning. Wasn't sure if de-aeration would have any affect on this. Its not loud just because its deep, can hear throughout the property faintly
Boiler and radiators are all otherwise spot on. Just minor irritations (possibly to the neighbours too as live in a flat)