Hi Lizzy,
Have a look at the following site http://www.sealskinz.com/
I've used their socks for running and biking in wet and really cold conditions and found them to be superb.
My feet do get a little sweaty in them but they stay warm and, if it's raining or I'm running hard, they'd be damp anyway so the advantages outweigh that particular disadvantage for me.
On another issue, since you're based in Iceland, I'm looking for an overseas marathon to run and have been considering Rekjavik (sp ?)
What's the area like for scenery and would it be a motivating race to do, do you think ?
Cheers
Bruxy