Hi, roof helmets do tend to be a bit noisy, shame you weren't impressed with the rossi one, as I'm an agv fan, it wouldn't be worth having your inner cheeks and headling replaced would it? It's fully removable on your helmet..
I was going to suggest Shoei too, but if that doesn't fit, then maybe you could try helmet painting anyone that fits providing it's not the cheap poly one that you buy.. I know someone that would do it for you, but I now see you live in Cornwall, so guess that's out of the question...
Incidently, have you tried more than one AGV or Shoei on, as you know they have different head shapes within their range, and it's so easy to rule a brand out if you've only tried just one! maybe try again...
good luck