Sorry Smick _ I hadn't noticed that you had already suggested parking round the corner
I guess the a23 right turn onto A205 delay you mentioned is due to the law of unintended consequences. Also, because I assume that is all owned by TFL, there are added cross-jurisdiction complication. Perhaps they will change the phasing of those lights - but that would then impact the straight over traffic on a major junction.
Maybe it will become faster to carry on down brixton hill and take a right on Upper Tulse HIll, or Somers etc and move onto the south circular that way (Or cut even more of the "corner" and go Leigham Vale -> Avenue court road: I do feel sorry for Leigham Vale / Hitherfield school). New short cuts will evolve in time, people will complain and they will eventually also be blocked
No expert, but I'm imagining traffic like water: it will find the path of least resistance, and if it sits around too long some will evaporate.
Also - I'm sure this has been mentioned up thread, or on the mega Brixton LTN thread - but
here is a map of all the comments - so you can zoom in and see if your neighbours' opinions match your expectations of them