Are we talking about the same United Kingdom as the one where Yougov has been doing polls on the subject of extremism [1]? If so I wonder what gives you the impression that the bulk of [y]our issues are growing far-right, nationalist, and/or authoritarian groups given that those who answered those polls come up with the following ranking:
#1 islamic extremism (58%)
#2 right-wing extremism (31%)
#2 left-wing extremism (23%)
Unsurprisingly the results differ widely based upon the political affiliation of the interviewee with left-wing voters placing larger emphasis on right-wing extremism while right-wing voters do the opposite. Nevertheless, left-wing extremism seems to be almost as 'popular' as the right-wing version while both are far less 'popular' than islamic extremism.
[1] https://yougov.co.uk/topics/politics/articles-reports/2021/0...