Martin Ellis, Halifax economist, said: "There have been significant population movements across England and Wales during recent years. Coastal areas have proved to be popular destinations for people to move to as many people have sought to take advantage of the benefits of living near the sea.
"The figures also highlight the transient nature of the population in many of our major cities. Birmingham, for example, recorded both the highest level of internal immigration and emigration in England and Wales."
When considering domestic migration, global cities (in the above case, London) are often net losers. Talent may move from one city to another, but this relocation decision doesn't support the Spiky World thesis. The Flat World is what makes utopia hunting possible. Plenty of people would escape New York City if they knew how to maintain their current line of work.
On the other hand, international migration is decidedly spiky. The costs of crossing borders demands a big return on the investment. If you are going move halfway around the world, then you might as well land in London. The move to the coast (or Pittsburgh) can come later.