Country TLDs are sometimes restricted to having to live in that country...Do you mean .co.uk? or just .uk? -- You have to get them through different registrars sometimes (just like .ca)
Because that is the way the UK decided to manage their domains. If you are going to have a commercial website, you have to register under .co.uk
Yeah doh, they ARE the ultimate registrars. End of story is, .uk is not a valid tld open to registrations.
All uk domains are actually subdomains. The TLD is .uk and co.uk, me.uk and org.uk are subdomains of that. Nominet hold the .uk domain extension and sell subdomains of this. I guess it's to make the .uk extension go further in terms of domains available and to stop confusion.