Nothing much standard, apart from examples like the polychrome GNR brick. Large companies like the GS&W made up of a hodge podge of smaller companies of varying means, constructing buildings at different times and going to different contractors and architects.
Some GSWR branches do have buildings, not really identical, but variations on a theme, say on the Kerry Road.
The GSR did do a line of signal cabins with a family resemblance though.