Helmet size?

It's really important to buy the one that fits you right, and has the features you need. Buying abroad may be a good bet, unless you can get to a big UK shop with lots of brands.
My helmet a Boeri, has ear pads which are detachable leaving a mesh covering over the ear. After the 1st week of wear I have not used the ear pads, and always have the top vents open. Hearing is not an issue with modern kit, fit is everything, some have an internal lace system, some have moveable velcro pads for adjusting the fit, but the shell shape must suit your bonce above all :D

As Bandit said you should really try it on. Each manufacturer seems to have a slightly different shape.

Infact I can see the day where ski shops have helmet fitters as well as boot fitters.

8)One the problems with helmets I am reminded of this winter is the one of tan lines. No more the classic racoon tan of the ski bum. Instead, a weird pale around the gills look, with lily white skin where your sideburns would grow with brown cheeks and nose.

trencher

i would sacrifice the colour of my burns (not that i can grow any) to keep the noggin in tact!!

Have a look at Smith Variant Brim

http://www.smithoptics.com/Variant-Brim_72_480.html

Not the cheapest, but a fantastic piece of kit IMO. Adjustable, removable ear pads, lots of vents, looks well smart and also so comfortable and light to wear I forget I've got mine on.

Mine's a Giro G10. I thought that wearing a helmet would be annoying, but now I wouldn't be without it. I got it after hitting my head in a nasty fall on ice. I went straight to a shop and tried on almost every helmet they had until I found the one that fit the best. It's surprising how much they vary even at the same size.

I have no problems with hearing in it, even when I have music playing (at a sensible volume) via the Tune Up earpads you can get for it. When very cold I wear a super thin balaclava under it.