Worker bees OR where are all the Brits

during the last several times I have been to London, it has been noticble that most of the workers in the public areas are not British. For awhile, they were Indians. Now it seems that a good many of them are Eastern European, Filipinos, and other nationalities I can't identity. Are there a lot of just English British people left working somewhere else? have they gone to other countries to work? who's left working in Eastern Europe and the Philippines? How funny that some of my friends in living in those countries are British.