Citing Azor in one tiny part:
There is emigration by White Britons from the UK (typically to Canada, Australia or New Zealand)
There has been a steady exit for many years now of white Britons, usually those with a ready skill needed abroad. A smaller number of ethnic minority Britons have gone too. Most simply see elsewhere as offering better life chances.

Their destinations are far wider than the 'old' Commonwealth, although some pass the entry procedures. For example 200-250k Brits reside in the Gulf states. Considerable number of English teachers are scattered across the world. Of the two million UK citizens living in the EU (cited this week), one million are working.