With all this talk of South Pimlico and modelling the railways of London, can I throw a new subject in here. I don't know whether it counts as a cliche, or just bad practice, but what about people who build layouts which they tell us are based in London, but look more like Leicester?
It's not hard, in London we don't have a lot of stone, we don't have nice hard red clay beds, and we don't have ready access to slate quarries except for the most affluent of 19th century builders. Most of the railway infrastructure was constructed of porous yellow stock bricks which absorbed all the smog and went black (although as usual there is a prototype for everything with the stone cutting outside St Pancras), Stations were often built of the same materials, unless the company building them happened to have ready links to the midlands to import hard reds. Often domestic properties were tiled rather than slated, and did not have a straight front to back pitch, but followed a valley roof profile. The roof pitch generally was shallower than houses in the North too.
Sorry, that was about to become a rant, so I am going to retire back to my proper work and see what you guys have to say.