Freight workings in the London area

[saltworth]

Hi there chaps, just getting back into the rail scene as my son has now rekindled his interest with him dragging me all over the country not the other way round!!
Long time since we visited London gricing but we are particularly interested in freight workings. Can anyone tell me the busiest places on a Friday. I know Acton used to be excellent as did Willesden on the High level platforms but with changing times has this all ceased. Any suggestions of where to spend the time between a Clapham Jct rush hour (am) and a London Bridge rush hour (pm) would be great