Just for information, the latest guidance on the export of cultural objects post-Brexit has been released.  See link

https://www.gov.uk/government/publications/exporting-objects-of-cultural-interest-if-theres-no-brexit-deal?utm_source=57d997e6-e76b-47a4-ab8c-8a3ff7ef0599&utm_medium=email&utm_campaign=govuk-notifications&utm_content=daily

Cheers, Neil