Right you wonderful eagle-eyed lot: this is the current state of the research thanks in great part to your most excellent observations.
Just over 50 Network Rail stations are sporting totems on (or near) platforms. Plus just over 30 others are blessed with beautiful artworks by Lionel Stanhope very close by (often on under bridges). Lionel has also made a dozen more murals inspired by the Gill Sans lettering (but not in totem shapes).
So almost 100 locations where exposure to designs that are over 60 years old are still very much seen by today's rail passengers.
The upshot is: not only is the the 1948 totem shape devised by A.J. White sought after by sign collectors, it is very much to the fore in 2024!
(If you have any suggestions of others I've missed, always happy to update this spreadsheet. I recall one in York for instance but wasn't able to find it last time I was there.)
* I'm also compiling stats for Heritage Railways and use by our Railway Modelling friends (if anyone is interested, I'm happy to pass on those findings also).