I can post one of the main building if you want
That is excellent, thank you. If you could, as you say follow up on that, I'd certainly appreciate it, as I'm sure the OP (Ken H) would, reading his first post. Thank you. The date of this plan being circa 1920 would have been the point that marked the completion of the major rebuild, that which started about 1898 ish and continued throughout WW1 in various stages until the 19..teens, as referred to in previous posts, and how the station then largely remained until the late 1980's when work started to provide space for the International platforms. I find it a fascinating subject, having played very minor parts in the train plan to infrastructure interface in more recent times, which did involve certain changes even before the 10 car suburban railway came in to being.
As for the 1885 North station extension (that which we latterly refer to as the Windsor side), although veering slightly OT, this may still interest some who have followed this so far. The SWC booklet 'Waterloo Station circa 1900', the (now) rarer to find publication I mentioned in post #2, there are some very fine photos and detail about the 1885 part of the station. One shows an Adams 'Ironclad' 4-4-2 tank loco standing in front of the older wall that formed the platform 16 side of the 'Village' offices (or platform 7 as it originally was from 1848 I believe), and (crucially) makes the valid point that this wall, prior to 1885, was the Northern outer wall of the entire station, hence its ornate architecture. Then the new Northern outer wall from 1885 on, once the Windsor side as some of us knew it (p16-p21) was completed, contained much plainer, rectangular windows, which is evident in said book and in a picture I took.
This is how that part of the station largely remained until demolition in 1990. A couple more of my own images here. Note the row of B.R.U.T.E. trolleys seemingly still in the same place on p21 in both images, and hanging on for dear life in the derelict remains of the latter image.