Speaking of Gatwick Express, I remember waiting at Ore for a terminating train to come out of the sidings and take me to Lewes. It was showing as twelve carriages on the destination display, which I thought was unlikely given the length of the platforms along the route, but I was prepared to believe it.
In came the train... and it had four carriages.
Also, yesterday, I was waiting at Paddington to get a friend of mine onto the 1700 to Temple Meads. We turned up 20 minutes before the train was due, and the platform hadn't been announced. It was booked on platform 1, and there was a train in platform 1, but, as there seemed to be disruption, and there were lots of people on it, we weren't sure. After speaking with several members of station staff, including the guard, the displays on the outside of the train kicked into life ten minutes before departure, which confirmed it was the 1700. When I left the station at 1652 to catch an EL service home, the displays on the platform were still showing "preparing" (though the platforms for the 1702 and 1706 had been announced...) - thank goodness platform 1 isn't gated! There is a reason I'm fairly often asked by friends to help them navigate the railway, and it's not because they like me
I suspect navigating the railway would be a lot easier for people if they operated by the rule of "if in doubt, ask a member of staff, if possible the guard", but equally the technology that is allegedly making certain areas of their roles obsolete needs to work properly first.