Movements between Great Britain and the EU will be controlled from the 1st January 2021, therefore a movement will be subject to customs, safety and security declarations, export controls will need to be considered (such as Dual use licensing, cultural goods licensing, etc.).
Plant and animal based products will require health or phytosanitary certification which includes wooden packing material that must now meet ISPM 15 standards.
Northern Ireland will remain part of the Customs Union and will continue to enjoy free movement into the Republic of Ireland but at the same time free movement into the UK.