DeSTiNeThese socks are made in the USA and have a lifetime warranty, so it might be that the company does not want to do deal with customers outside of the US if they have to use the warranty.
litesportI'm not sure, all I know is that if you buy directly from Darn Tough, they do not ship outside of the US. Also, I checked the Amazon.co.uk sellers and they are not listed on the Authorized Amazon Amazon Sellers list.