England was 50 years ago a much more English place, with less than 1/2 a percent of the population being immigrants

150 years ago there was mass immigration of Irish people to England. The influx caused great anxiety about cultural (and literal) pollution - they were thought to be degenerate, disorderly, diseased and generally a Very Bad Thing. 150 years on, most of their descendants don't even have an Irish accent.

100 years ago there was mass immigration of East European Jews. Again, the newcomers were thought to be a Very Bad Thing. Again, they responded by getting jobs, getting married and generally settling in. Again, 100 years later their descendants are as English as you or I.

Why should you be worried that this process isn't going to happen again?