I don't know how up to date that is from a legal viewpoint either ... but it's commonly accepted that inhaling of just about anything (except air and medical inhalers) isn't allowed. You'll find people standing just outside the station gate or being very secretive on the platform.
From last week (note - Scots law may differ to UK law and this is Kirkwood station in Coatbridge). A dark, cold, unpleasant place to wait 45 minutes for a train in a gale when you arrive for a train that's been cancelled.
The suggestion here is that it's also illegal not to report someone who's puffing on an e-cigarette on the platform, let alone to puff yourself. Can't say that I fancy the idea of calling in on the help point within clear earshot of a group with "smokers" amongst it, to report them for smoking - "asking for trouble" comes to mind as does "being an interfering busy-body" on a gale swept open platform with hardly anyone else around.
