"Actually I find you get more wind noise with the flying helmet. Seems strange I know. Perhaps other users can comment"

I'll agree with this - the wind rush on the edge of the ear flaps seems to be the culprit. I wear earplugs if I'm above town speeds anyway.
Side benefit of keeping in the ear plugs in town is you can of course use higher revs and more throttle without seeming overly loud... smile