Great Question Scott. This particular domain has stumped several other people.
uk.com is not a valid cc tld. The proper cctld for the uk is .co.uk. What you're looking at is two-letter rootdomain on a .com. It's just like shoes.com or anything else. People can basically buy subdomains from the owner of the uk.com rootdomain and host their websites there. As you can see, it's a clever strategy because they get alot of diverse incoming links from all the subdomains they sell on their root domain. Pretty clever, huh?