Nominet, the central registry for .UK requires that a "registrant" contact in the UK is set when a domain is registered. You can also set up this information within your Dynadot account by following these instructions:

1. Sign in to your Dynadot account.
2. Select "My Domains" from the left-side menu bar and click "TLD Settings" in the drop-down.
3. Click on the "UK Domain Settings" link, then click "Create Contact Record".
4. Enter in your .UK default admin contact information in the provided form and click "Save".

NOTE: This is not required for .CO.UK, .ORG.UK, or .ME.UK domains.