'Buy British!' we often hear, and many foreign companies have done just that. US food giant Kraft bought Cadbury in 2010, Dutch group AkzoNobel acquired ICI in 2007, Deutsche Bahn now own Arriva, and that's just the beginning.The truth is that hundreds of billions of pounds' worth of British businesses have been sold off abroad in recent years. But what does this takeover bonanza mean for our future economic health?In Britain for Sale, award-winning financial journalist Alex Brummer investigates this question, explaining why British companies are so irresistible to overseas buyers and weighing up the true cost of these transactions.