People in the business of producing physicals goods will have to comply with both EU and UK regulations. Should they desire to export something to the EU, the amount of paperwork will go up, possibly by a lot, to deal with rules about country of origin and such things. If you want to export services, good luck! You will need a work permit and can, at most, stay for 90 days in any 12-month period. Also, any professional qualifications or licenses will have to be obtained for whatever country you plan to work in. You’ll need a visa to study in the EU, and the UK will no longer be part of Erasmus. Northern Ireland would appear, by and large, to be more aligned with the rest of the island than with Great Britain.