There's nothing official south of the Thames, but in all of the areas you've mentioned I've seen plenty of ugly crack whore street walkers looking for business....They're usually never dressed like tarts or working in groups, but you can't miss the strong eye contact they're making with men walking past & cars driving by.
Not to mention a ugly
woman on the street late at night not obviously going somewhere is a dead give away.
I can't say there's definitely one place you can go and find them every night like you do in Newham or Southall with the Romanians. But on the brixton hill between the two sainsburys locals theres usually something there.
Never picked one of these girls up myself nore would I want to.