I've been using a pair of Sealskinz mid-thermals and they have been great but are just starting to let in. I think I paid 20 notes and consider that good value for 6 years of dry feet.
Anyway, I started searching for a new pair and found some Seal-Skinz long-lites on the Uttings Outdoors site. Unbelievable, RRP 35 on offer for 10. Ordered yesterday lunch time and they arrived today. Postage was a fiver but as I got a pair each for me and a mate I didn't mind paying 25 quid.
So, if your boots are a bit leaky, just carry a pair of these with you. Although they claimed to be breathable, I did find the old ones made my feet a bit, er, hot, shall we say. All in all, I'd recommend the socks and the deal.
This has been a public service announcement.