I can understand some of the confusion....
We, as a nation (the UK, that is), have no real identity.
British Isles - An archipelago in North Western Europe. Including Great Britain, Ireland, Hebrides, Shetlands, Orkneys, Man and others (does not include the Channel Islands, no matter what the jersey tourist board say). The term British Isles is controversial in Ireland though, as it implies UK ownership over the whole archipelago.
Great Britain - Not a country, but the largest island in the British Isles. Includes Scotland, England and Wales, which together make up 3/4 of the United Kingdoms constituent nations.
Ireland - Not a country, but the second largest island in the British Isles. Includes the nation of the Republic of Ireland and also the Northern Ireland part of the United Kingdom (which is technically the sole surviving part of the Kingdom of Ireland).
United Kingdom of Great Britain and Northern Ireland (or UK) - A nation made up of the whole of Great Britain, plus the northern part of the island of Ireland. It's capital is London, the head of state is HM Queen Elizabeth II, and the Prime Minister is Gordon Brown.
Scotland - A constituent nation of the UK, taking up the northern 1/3 of Great Britain. Many, many miles from London. Has devolved powers, and is self-governing in respect to domestic policy. Immigration, defence and foreign policy are still handled by the UK gov. Also includes most of the islands on the northern and western coasts of Scotland.
England - A constituent nation of the UK, taking up the southern 2/3 of Great Britain. This contains London, though London has many devolved powers and is becoming increasingly self-governing.
Wales - A principality of the UK, on the western side of England. Was annexed by England long before the act of union, and has only been recognised as seperate to England in the latter part of the 20th Century. Is largely self-governing, with a strong gaelic speaking community and identity.
Northern Ireland (or Ulster) - A province of the UK. On the NE part of the island of Ireland. Is populated by a majority of Scots protestant descendants, which is the primary reason why it did not gain independence at the same time as the catholic dominated Republic.
Republic of Ireland (or Eire) - A sovereign nation, taking up most of the southern and NW parts of the island of Ireland. Has not been part of the UK since the early part of the 20th Century.
Isle of Man - Not a part of the UK, but a self governing Crown dependency.
Channel Islands - A chain of islands of NW France. Not a part of the UK, but a group of self governing Crown dependencies.
Now, try explaining that to our colonial cousins.