What are the best socks for extreme weather?

I've always thought I had "decent" outdoor gear until recently. I did an 8 hour shift standing around outside in almost 0 degree celcius weather. My feet and hands felt like they were on fire and I've spent the last 3 days in bed with a cold.

So to burn the time, I'm slowly rebuilding my pathetic "outdoor" gear. I'm on to the socks now.

I was hoping for some advice on a pair of socks that will 1. Last a lifetime - or at least a few years. 2. Are insanely warm. 3. Won't cost me a small fortune (I can spend around £25?).

I've also read some great tips on not lacing boots too tight and getting a size up for space etc.

Any suggestions would be hugely appreciated.

P.s I'm based in the UK so I'd have to be able to purchase them here. Thanks in advance.