Transferring a .CO.UK domain works slightly differently than most domain transfers. You would not go through the conventional transfer flow, using transfer codes, but instead .CO.UK uses IPS Tags.
You will first need to contact your current registrar and ask them to change the domain’s IPS Tag to Name.com’s tag:
Once they have changed it, send us an email at firstname.lastname@example.org from the administrative email address on your account, and let us know your username and the domain name that you are transferring, so that we can insert it into your account.
Note: The transfer of a .CO.UK domain is free of charge, but it does not include a renewal of the domain name.