In the mid seventies we took in a huge swathe of refugees from Uganda,
They're a minority of the Indian population in Britain though and the Indian community had already been established in Britain for decades before the arrival of what were essentially refugees from Uganda. They wouldn't be very welcome today, would they, the old 'fugees'.
Is it because the British have always chosen the most promising immigrants from India and rejected those low-skilled?
No that's not the case at all and it continues to be a source of debate as to why the Indian immigrants have been such a success story whilst those from Pakistan and Bangladesh less so. The younger generations of Pakistanis are actually starting to catch up now, achieving better educational results etc. Of course though, there have always been Pakistani success stories too. This guy, James Caan, came to England as a toddler with his parents. His father spoke no English, the usual story but built a successful small business and Caan (who changed the spelling of his name from Khan) is now one of the richest men in the UK. Caan is from the Brick Lane area of London, same as Alan Sugar. He's talking about an interesting topic here:
youtube.com/watch?v=hWXb8CJE7ic