Here's an idea. At stations with this type of problem (trains not stopping where passengers expect them to, to simplify things) which are also provided with many dot-matrix information boards above/beside the platforms, how about having a flashing message saying something like "Train stops further down platform - please move down"? Perhaps this could be as part of a phrase involving the train's details, if more than one service may need to use the platform.
So, for example:
Code:
1st 1020 London Bridge 1020
Southern service. Formed of 4 coac
* PLEASE MOVE DOWN THE PLATFORM *
If there is late running of a service:
Code:
1st 1020 London Bridge 1033
1020 LDN BRIDGE TRAIN AT OTHER END
2nd 1034 Reading 1034
(Currently, the display may or may not indicate that the train is scheduled to leave from Platform 1a or 1b, for example, but this information may be hidden in reams of scrolling text and it is not clear exactly what passengers are to do with the information.)
Some termini have such a concept within their automated announcement system for occasions when more than one train is in a platform and passengers must walk down to board the correct service.