Sorry I missed out a NIcation for the whole UK.
Thinkin' on, I bet very few have a full UKcation. If you visit NI you might travel from Scotland, England or Wales for a ferry you're unlikely to pass through all four nations. Theoretically someone from Wales could ignore Holyhead, Pembroke and Fishguard and drive into England and up to Stranraer to get a ferry across to NI. That would be a real UKcation.