Some people may have used a Canadian registrar to register .uk domains so I am mentioning this here without any reference to the registrar.

Nominet, the UK registry operator, is now checking all of their registrations and will cancel any domain name registrations with invalid contact information. There have been some issues with improper registrant information in .eu domain registrations made by a particular registrar so it would be prudent for people to check any .uk domains they hold to ensure everything is correct and that the account information at their domain registrar matches the public Nominet WHOIS information.