OK thanks. By the UK, do you mean Great Britain? England? Something else?

As far as I know (admittedly not far), Christians in the UK are about one-third Church of England, one-third non-denominational, one-fifth Catholic, and the rest other. I think most of the growth in non-denominational Christian churches in the UK has taken place in my lifetime.

There is a particular part of the UK where, in fairly recent decades, I think self-identifying as "Protestant," as quite specifically opposed to "Catholic," was not at all odd, to use your word. Not sure of the extent to which that's still the case.