Afro/Asian population of France in 1950: ca 60 000; 2010: ca 6 MillionAfro/Asian population of Britain in 1950: ca 50 000; 2010: ca 5 MillionI call that mass immigration
The large majority of the African population in France is a result of immigration from the states that made up the French portions of Northern Africa (particularly Algeria) during the independence period, and they only constitute around 4 million.
I'd also point out that of that just as many European descended Africans moved to France as did Arab Africans.
In the case of Britain only 4.7% of the population is Asian (the vast majority of which are from the Indian Sub-continent) while only .8% are African.
A good deal of that to is something that has happened over the last 20-30 years, not something that happened right after WW2.
Also, like the United States, Britain has a long history of immigration, with African and Asian populations that go back three centuries, so natural growth plays a factor in it to.
In general I also question the accuracy of those numbers, and really, an increase of 3 million over half a century is not mass immigration, if you want mass immigration look at American history, where we saw the population increase, which in a single 50 year period saw a population increase of roughly 53 million people, the majority of which was the result of immigration.