Some very interesting on-topic responses to this thread on the first page - thanks to those who contributed! The off-topic ones are also interesting, although perhaps in a train-wreck fascination kind of way.

To try to counter the Balkan pessimism, I would just say that national animosities can fade, sometimes surprisingly quickly. England and France may be an old example. Relations between the former Axis countries and their WW2 opponents a somewhat more recent one. Rosacrux, as an English person, I don't think it's true to say hatred exists between the English and either the Irish or the Scots. I've never seen evidence of it, anyway. Local animosities in Northern Ireland are worse than those in most of the Balkans, it's true, but at least the fighting has stopped. My impression is that people from the Republic of Ireland and mainland Britain made their peace some time ago. The Scots seem quite content to be ruling England from No. 10 and No. 11 Downing Street, while the English don't notice.