Thanks again, Dan.
I visited Allan Jeffries and tried the Sys 5. It didn't work for me - too much like a goldfish bowl. Undoubtedly a nice product with good fit and finish, but not right for me. I think it could have been improved by additional padding around the ears (it felt very empty) but they didn't have any spare pads.
I then tried on the Sport Integral and it felt perfect. I know it is a completely different type of lid and I shouldn't make direct comparisons. But, it felt right, so I bought it. Only £185 too, which was a pleasant surprise.
As soon as I finish fitting my damn spotlights I will be off down the road...
As a final thought on helmet noise, I am absolutely convinced that a major factor is the height dimension of the helmet. In other words, how much helmet continues down beyond your ears. The more the better it seems. I know screen aerodynamics is the overriding factor, but a 'short' helmet seems noisy even without a screen.
Cheers
Glynn