Very interesting article!
Reading "between the lines" of it though, it may not be as simple as the UK being a Hub.
It looks, at least to me, like some of the people are returning home, as stated here:
Australia was by far the most popular destination, with 100,000 heading Down Under, Australians returning home after working in Britain and UK nationals emigrating. Some 56,000 people moved to Spain and 40,000 to France
I guess that some of those going to India and Pakistan are British nationals of Asian descent, but would count as UK nationals leaving.
Maybe instead of it being exactly like a Hub, some of those could be classed as Generational Rebound. Maybe those who've worked here for 40+ years, earnt their money and are returning to the land of their birth. Maybe they're 2nd generation and are returning to discover the land they came from.
Of course, there are those leaving for the obvious reasons such as better jobs or better weather. But it'd be interesting to know what the exact breakdown would be of those leaving. As usual, UK statistics leave a lot to be desired in what they don't tell....
Interesting none the less!