This is a Second Level Domain managed by Nominet UK.
You can check Domain availability here.
The Terms and Conditions can be found here.
IDN is NOT supported (Special characters like å, ä, ö).
The contact information provided for this domain must have a valid Name and Address residing in the UK. This data is validated by Nominet UK later, if they determine it is not valid the domain is suspended/deleted.
If you want to transfer a .CO.UK domain to us, read this guide first.