If "Wanted Down Under" is anything to go by, British-trained nurses and their plumber/sparks/builder husbands are heading for Oz or the States, in search of better rates of pay. Our brain-drain is creating at least some of these vacancies, so we are 'brain-drain'ing some less well-off parts of the world.
@O_G,
If you move 10,000 people from dozens of countries into the UK, to do x amount of work, you'll need another 1000 or so to service the needs of this small 'town', which wasn't here last year. In my books, there is economic growth in that last 1000 (service industries).