In message , at 23:27:31 on
Fri, 2 Nov 2012, Jarle H Knudsen remarked:

There is no specific number of standing passengers permitted, basically as
many as you can fit. So there is no standard figure that could be used.

No health and safety rules?

There have been isolated cases of train guards refusing to move a train
with people in the vestibules, but 999 times out of 1000 people will be
allowed to stand on every available bit of floor.
--
Roland Perry