I've seen some mocking it, which would
generally be exempt from copyright claims under the parody exception.
For example:
https://aml-group.com/app/uploads/2019/07/3.mix_.png (I have linked to the image rather than posted it inline as there's a swear word on one side). The image is from a set of pub toilets, with a picture of a toilet accompanied by the text, "If you pee somewhere that isn't right. Clear it up. Don't just leave it. Pee it. Spray it. Sort it."
I'm sure I saw a pub or coffee shop with an A board outside which had a parody reference to it but can't remember what it was.
I think I've also seen a folkawolf mock advert based on it, but can't remember what/where that was either.
It seems a bit lazy to tweak then reuse the slogan in a genuine sense, but I suppose the overriding points for me would be - if it gets the message across and changes even one person's behaviour, fair enough; and that I can't see a public interest in the BTP pursuing some sort of copyright claim; it would also be a bit of a bad look I feel trying to 'shut down' a football team's anti-discrimination campaign poster.