Your feet are going to get wet and cold eventually whatever you do if it's wet and cold enough. My full armoury consists of (by layer): thin thermal sock, water resistant tights, Porelle drys, Shimano winter boot, & water resistant neoprene overshoes. Don't usually go this far though, and I bought my winter boots a size too big to retain circulation.

Sorry short attention span, so if this has been said ignore me.

Diadora do a great waterproof mtb boot.

And i can't bring myself to spend £20 on a pair of socks so use freezer bags on my feet, over my socks. Yeah, very pikey but seem to work as well as mates with expensive socks.I am in cornwall though,which isn't known for very cold winters,wet but not cold!

I am about to buy a pair of Gortes shocks to wear over my normal socks. I have tried the Sealskin socks but did not like them. The trick is to ensure that the shock combination is not too tight in the shoe (as mentioned by someone else) or your feet will be colder due to lack of circulation.