Thought I'd bump this in anticipation, and share some basic research. Bachmann are doing five types, based on Diagrams 329 (TK), 332 (FK), 328 (CK), 346 (BTK) and 345 (BCK). These were all built with square-cornered windows up until 1948, and round-cornered ones from 1949 - Bachmann are doing the square ones. The respective numbers built were, roughly, TK 285 square/167 round, FK 22/67, CK 49/61, BSK 36/46. BCK, 30/10.
Interesting that there were twice as many square-cornered TKs as all the other square-cornered types put together. Also noteworthy that the square-cornered BSKs only just outnumbered the similar BCKs.
Looking forward to these, and crossing my fingers that the crimson and cream isn't that far removed from Hornby's Gresleys.