I made that claim and I stand by it. Britain in 1945 was effectively broke and seeking to plug massive holes in its workforce. That’s the context in which Britain spent its Marshall Plan money trying to support the flagging empire:
http://www.bbc.co.uk/history/british/modern/marshall_01.shtm...I’m afraid I don’t understand the logic behind what you’re trying to say regarding the relationship of GDP and immigration. Obviously net inward migration can only raise the total GDP of a country. The question of what happens to average incomes is much more nuanced, but there’s a fair bit of evidence that low paid workers can be hard hit in the short term, whereas everyone benefits in the long term: https://fullfact.org/immigration/immigration-and-jobs-labour...
I am not suggesting that you’re a racist or anti-immigration, just that your views on the relationship between GDP and immigration are wrong. Besides that, they do nothing to refute my original point that we should not have different classes of citizen based on race and geography.