I haven't paid much attention to BLM UK, but I live in an incredibly ethnically diverse area. Though I don't know of brutality that has occurred, I do understand that the stop and search police power has been abused, especially with young black males. Though more common of teenagers that are suspected of having some sort of antisocial behaviour, I have witnessed an 11 y/o getting frisked rather roughly, and he wasn't being antisocial in the slightest. I remember some boys in our class talking about being stopped and searched in year 8, and even though they weren't model students at all and could be very rowdy, they didn't strike me as violent either.
Now, I have no stats or facts to back this post up, because I honestly can't be bothered to search for any. Therefore, I could have a distorted view just because it's more concentrated around me. Regardless, I do see why there might be such a thing as BLM UK though according to stats from OP's post it isn't very necessary.