As mentioned, the aim would be 95-98% racial homogeneity, which is roughly what Britain was about 40 years ago. Even as recently as the mid-1980s you can look up footage of London and still see nearly all white people walking the streets and travelling on the Tube.

The priority would be on deporting scum and repatriating more recent arrivals and their offspring. I think once you deported/repatriated these people, we'd be very close anyway. The tiny black community who have been in Liverpool for 150 years (or however long it is) aren't a problem.