Dogging & Train Dogging in London East London

I am looking for info on dogging sites in London East London and or anyone who does Train Dogging out of Liverpool Street. (Train Dogging is when we use the trains, train lo's, train station carparks & surounding areas for meets). I was part of a Liverpool Street station - Southend dogging group until most had dropped out. Anyone outthere interested or know's of places to go? Thanks, D