In reply to Migsy:
I'm also a great fan of the Ecrin Roc.
The right cog adjusts to the size of your head, and the left cog adjusts the straps to the back if your neck.
If you mean adjusting the internal bit that sits *on top* of your head, I don't think that this is possible (I may be wrong), as I'm pretty sure that the distance between your head and the plastic of the lid itself has to be that much to allow for the shock of something hitting the helmet and not transferring through to your bonce!
Mine sits pretty high on my head as well - I think that's just the way it goes, you look a bit silly, but that's a small price to pay if you get hit on the head!