Completely anecdotal but I raised the BBC report amongst a gang of friends over the weekend representing 3 congregations and we all knew of a case in each of our halls in the past 20 or so years. We also knew of another serious case in a friend's hall. I also know of a case in a local congregation that is not known about publicly and I have no idea if anyone in the congregation has been warned. There are some particular circumstances around the case but I know the person concerned goes to meetings.
This of course is related to people known to have committed abuse. We've got no idea if there is anyone else around that is either not known, never been convicted or otherwise.
It also is nothing to do with cases that have made the news over recent months.
My personal opinion is that I find it unlikely that there is as many as 1 or 2 abusers in each congregation of roughly 100 in the UK but 1-5 per circuit would not surprise me at all.