In the US I think that "platform" has the very literal meaning of a raised platform, level with the railroad car, allowing you to step into the train without climbing steps. The station isn't a "platform." A platform is part of a station. Twenty years ago platforms were found only at larger stations.
In other words, "platform" is to "train" as "jetway" is to "plane."
In the United States, boarding places are referred to by "track numbers," not "platform numbers." It may be different in the UK. The usual announcement would be "The 5:15 train to Forge Park is now boarding on track 8."
In order to serve people in wheelchairs, all of the stations where I live now have short platforms, just long enough to serve one car. In the middle of the day when not many people are riding, they may have only one car on the train open, and you may hear an announcement "Please board the train at the raised platform."