Why don't British people like to call them British?

It's not that I don't like it, but I don't know who the British mean. All over the world, we in China call them Englishmen, and they call themselves Englishmen or Englishmen, which is omitted when we call it convenient. Needless to say, we call it Britain. The full name is: United Kingdom of Great Britain and Northern Ireland. If they meet for the first time, they really don't know when they will become' foreigners'.

The English are descendants of the Anglo-Saxons, while other Scots, Irish and Welsh are natives and belong to the Celts. In addition, one believes in Orthodox Christianity and the other believes in Protestantism, so there are some contradictions, but they are not big, mainly with the Irish, followed by the Scots.