Might try sealskinz - only concern is i'll have to wash them every night as i'd probably only be able to afford one pair!
If keeping the cost down, then overshoes as you'll need more than one pair of socks, but they should dry overnight.
You can get different weights of bib tight fabrics, some have windstopper panels. In the real cold I use some Biemme Bibs, with windstopper material over the knee, front of thigh and around the kidney area. They work a treat, but they aren't cheap - £60 plus. If the temp is above freezing, I use standard roubaix bibs.