It has been that way long ago. Brought in by the left wing nutjobs of the UK government.
Still not as bad as the Midlands areas e.g. Birmingham.
If you go to the UK, stick to the touristy parts of the bigger cities, and if you want to go to 'countryside' places: far southeast (Exeter, Plymouth), East Anglia (Norwich) and the Peak District (mountain-park region between Manchester and Sheffield). Less chances of you encountering non-white imported 'diversity' there.