Paul wrote:

I think I've seen something on the scrolling display on a train. It
was only a glance but it didn't seem to show it again (until I got
bored).

Yes, it scrolls round between listing the destination and stopping pattern
(usually after station stops) and says 'All seats on this train are standard
class'. I made a note of checking it yesterday on a couple of W&E trains -
it ought to show more frequently though.