Just thinking about Scotland independence vote. Could see that kind of thing within UK soon depending on which way it goes. That is still a national boundary though.
It wouldn't be within the UK, since a 'yes' vote implicitly causes the UK to cease to exist.
It would be more like Norwegians crossing the border to Sweden to stock up on cheap beer - which already happens. I believe you sometimes see similar things in Ireland at the Northern Ireland/EIRE border, depending on VAT and currency exchange rates.
