Thankyou everyone for your kind comments. The "can you guess what it is yet" mode of presentation can sometimes be a little irritating for the reader, but I couldn't resist it here :-)
No, this is not the start of doing Paddington Goods, although it would be an immensely interesting project. As Buckjumper's research and project shows, there is so much potential for modelling the London area goods operations. Anyway I am just stealing the design of the Paddington cranes and using them in the Farthing goods depot as a way of hinting that this is a fairly large depot although we are only seeing a small part of it (which is also why I need at least one more crane).
Sasquatch, I think the wagons in the 1926 (actually 1927) photo carry the 16" GW letters, which replaced the 25" letters around 1920. The 5" letters were introduced in 1936. So that is as would be expected?
Doing something like this in plastikard and with ad hoc available items is fast and fairly simple. But it also involves compromises. For instance I would say I have stretched the plastikard to the limit here - now that everything is in place it is structurally sound, but there were some dodgy moments along the way when it looked like I would end up with a banana shaped crane! And there is the thickness of edges etc which only brass could get 100% right.
So there is an awful lot of good to say for the more exacting and laborious approach that eg you are talking about, Nick and Buckjumper: That to me is still the gold standard way of doing things and in due course we'll all admire the results! To me it's just a matter of finding the approach that suits me best.