In Britain, a policy of 'immigration' was started after the Second World War. Every government since has continued it, blind to its social consequences.
It may be argued, that just as with recent EU inward movement from the east, this has benefitted those with capital but disadvantaged the traditional 'working class'. This may explain in part an emergence of racsim in the latter but liberalism in the former.
Your experience Ben, I would suggest, is fairly typical of the psychological response by many to being 'swamped' by a new culture, distinctly different to the preceeding one. It was evidenced in the 'fifties' by the Notting Hill riots but of course an objection to 'invaders' can be traced back to earliest times.
The English character and constitution (note small 'c' but it applies equally to the big one) has taken hundreds, if not thousands of years to form. It no doubt has good and bad points but it is recognisable and distinctive.
'Multi-culturalism' may be the prevailing politically correct view, but just like Eurocentric ones, they may not reflect the predominant mood or spirit of the country, if such can be distilled.
As a result it has produced yet another gulf between the govenors and the governed. Immigration was seen to be an issue because it was too big and too fast and was proved to be out of control.
Any country can expect to have and keep a prevailing identity and there is an inchoate angst in Britain that it is losing its traditional values from a range of factors, of which immigration is but one.
On the up-side, we may well be more tolerant and caring in many areas of life and social policy than we once were. The history of a nation never stands still. Nor can the clock be turned back to some non-existant perfect elysian state and time, so we must cope with what we have.
But we must also be honest with ourselves and the problems that have been created by a naive approach to uncontrolled immigration policy, on the basis of 'multi-cultualism' rather than 'integration'.
Somehow in a multi-cultural world, with huge economic divergance, where modern media cuts through division like a butter knife, we still have not learned how to cope with the destabilizing consequences of a mass movement of population about the world, trying to escape poverty and violence.
Perhaps we need a crash course in how to do so?