There is a lot of confusion about the terms United Kingdom and Great Britain. This is unnecessary because UK is short for 'The United Kingdom of Great Britain and Northern Ireland.' Hence Great Britain consists of England, Scotland and Wales; the United Kingdom of these plus Northern Ireland.
It is worth noting, if you want to avoid bloomers with the residents, that neither the Channel Islands (Jersey, Guernsey, Alderney, Sark and Herm) nor the Isle of Man are part of either of the above entities!