Some real traffic planning failures cause most of those jams, unfortunately no traffic planner seems to have spotted them.

St.Dunstans - never used to allow cars to drop on its access road. About 10 years ago, they seemed to change that. Now, on a bad morning - cars can be solid on their "D" shaped road, then you'll get the paradox snarl up where arriving vehicles from the East are trying to turn right into the school, with a tailback of 8-10 cars. The lead vehicle trying to exit the school is trying to turn right onto the A205 and can't exit the school because of above mentioned tailback. Gridlock. Before long, vehicles are tailing back to the West on the A205 too, as they want to turn left into the school but can't. A205 stalled in both directions. Seen it, several times.
Unfortunately, the (lack of) quality of school run drivers (ahem) comes into play here and the exiting vehicle trying to turn right should recognise the problem and go left, but won't.
Solution - ban right turns into/from St.Dunstans, or make them close their access roads again. Little darlings could walk from drop offs on local residential roads, it won't kill them.

Another screw up - bus stops opposite each other by Catford Bridge station, with a permitted right turn from A205 into Doggett Road. All you need is a bus at the stop and someone alongside wanting to turn right and Westbound carriageway stops. Someone needs to stagger the bus stops or remove that right turn.

Ilegal right turns into/out of Wickes and Halfords. I think the traffic order is still defective there - there's no right turn into Wickes (Eastbound) but no prohibition into Halfords. Neither is well signed though and the principle of no right turn is correct and should apply to both.

Simple and obvious fixes.