Travelling into London on Saturday going past Neasden I saw an S stock with tankers and BR locomotives (not sure of class) at each end. When I was on the way back home it was still there but I noticed that the door in the middle of the cab had no window and was solid red.
For the answers to all of your questions, please see the "S stock delivery & introduction - discussion" thread, from this post onwards.
For bookkeeping purposes, I'm gonna lock this thread, if that's alright. Best to seek any additional clarification over there, to save on cross-posting or having information spread over multiple threads.