The .co.uk second-level domain name (SLD) is intended for any business either located or doing business in the United Kingdom. However, anybody can register a .co.uk domain name as long as it is available.
In order to register a new .co.uk domain name, the registrant must either reside in the UK or provide a UK address for service. P.O. boxes and their equivalent are not permitted. Nominet, the controlling registry for all .uk domain names, utilizes a data validation process that automatically attempts to validate the name and address data provided by registrants. If this data cannot be validated by Nominet, they will contact Uniregistry to undertake further validation activities (See section R3.37.2 of our TOS under the TLD specific terms as to how we will handle the requests).
Please note that Nominet will suspend a domain name if they are unable to validate the data within 30 days from a request. Registration terms for .co.uk domain names start at one year and max out at ten years.