Just in case there's anyone out there who hasn't discovered them
Poundland have "camping socks" @ 3 pairs for £1 (obviously)
I can highly recommend them
*Additional Tip 1
Take them with you to the rally in a "waterproof " bag along with a "micro-fibre" towel & a small container of talcum powder
The feeling of warm DRY feet is hard to beat for "bringing you round" after arriving on site with "soggy" feet (for whatever reason)
*Additional Tip 2
A couple of carrier bags*, slipped over your socks before putting on your "wet" boots, will allow you to "get out and about" onto site
Without soaking your socks again from the soggy footwear
Just dont leave them on for TOO long* or your feet will sweat and you'll be back to square 1
* The ones with holes in allow your feet to breathe a little
Hope this helps
Em