When the smoking ban came in, Lib Dems were split by the issue. You could legitimately use key liberal arguments on either side. I argued the point against Stephen Williams MP at a student meeting - I opposed the ban on the grounds of individual freedom to wreck your own lungs; he supported it on the basis that smoking in public caused unfair risk to others. We were both quoting Mill's famous harm principle on opposite sides of the same debate!
The whole thing was confused even further by the legislation itself, which defined "public place" very widely, including privately-run businesses that were open to the public. That made it even harder to find the dividing-line between personal rights and public menace.
The device that's now in the news is the e-cigarette, a fake cigarette which lets you inhale a fine mist of pure nicotine. Currently unregulated in the UK, various campaign groups (including ASH) are calling for selling restrictions similar to those in place for cigarettes.
The key difference between an e-cigarette and the real thing is that the e-cigarette poses no risk to others in the vicinity. It doesn't pump smoke, tar, or carbon monoxide into the atmosphere. The only person who might be harmed is the person using it. On that basis, I'd argue that any regulation should be very light. Subject to the usual health and safety rules that you'd expect, there's no good reason for making it difficult to get hold of and "smoke" these devices.