I doubt whether vaping will ever become acceptable in public indoor spaces. The smoking laws have been in force for a long time now and although you don't see No Vaping notices inside buildings, you just have to treat vaping as smoking.
When I enter my local Vape Store, to buy more juice, usually on a Saturday, it's like entering Dantes Inferno, as the whole shop is engulfed in vapour clouds. Can you imagine going into Costa Coffe and seeing people vaping, the place would no doubt be like the Vape Store. People would complain, like they would if people were smoking.
It is a matter of using common sense and wait until you are in open spaces before chugging on your vapes. As a matter of interest on this subject, P&O Cruises do have a policy on board their ships, regarding vaping.
Vaping is allowed inside your cabin and on cabin balconies. Vaping on open decks is only allowed in areas designated for smoking cigarettes & tobacco, where ashtrays are provided. Vaping is not permitted in all public inside spaces, including corridors on all decks.
So vaping is still treated as smoking, with the exception that you can use them in all private cabins. This is because they are not classed as a fire risk. Regarding cigarettes, when smoking on designated open deck areas, you are requested to put out your cigarettes in the provided ash bins and not to throw your cigarettes over the side of the ship. This states that the wind could blow any discarded cigarette ends into ventilation opening, thus causing a fire.
I think before too long, we are going to see notices requesting that you refrain from using vaping defices inside all public spaces, on public transport and other places where smoking is not allowed. Personally I treat my vaping as I would if I was still smoking and only vape outside. It is just a matter of considering others, who do not or have never smoked.