An electronic cigarette (‘ecig’ hereafter) is a battery-powered vaporizer which produces a similar feel to tobacco smoking. Ecigs produce an aerosol, commonly called vapor, rather than cigarette smoke, which the user inhales. Ecigs have a heating element that atomizes a liquid solution known as e-liquid. E-liquids usually contain a mixture of propylene glycol, glycerin, nicotine, and flavorings.
No. Though in the UK their use has not been formally prohibited, any location can prohibit their use if they wish. Please find more guidance here.
You can buy ecigs at many shops and supermarkets now. You can buy ‘vapes’, a more sophisticated product that many believe is better than an ecig, at most ecig & vaping stores. We would urge you to find your nearest store and ask to try out some options; this will be the quickest, easiest, and cheapest way to find which works best for you, and ensure you never smoke cigarettes again.
In our opinion, yes. Ecigs usually contain nicotine, and nicotine is a stimulant, not unlike caffeine in its impact. This can be useful, keeping you alert and ‘alive’. On the other hand, it’s probably not what you want when you want to switch off. In our experience, you should stop using ecigs and vapes around 30-60 minutes before bed. If you still want the hand-mouth thing, then consider switching to a clearomizer containing a lower amount of nicotine (e.g. 6mg), or even one with none at all. You will still get vapour, though less of a throat hit.
Many people ask are e cigarettes safe? The British Medical Association says the simple answer is that we don’t yet know. Ecigs are relatively new, and thus we will only truly know the answer to this from their human impact, probably decades away. There are many trials going on to try and find out more.

Because there are concerns over the quality of some of the ecigs on sale today in the UK, the Medicines and Healthcare Products Regulatory Agency will regulate e-cigarettes as medicines from 2016. This regulator has said “levels of contamination” have been found in some products and others have been poorly manufactured.

However, there is a consensus that they are certainly less harmful than smoking tobacco, which is responsible for 100,000 deaths a year in the UK.

We recommend this BBC Radio 4 programme from July 2014 which gives a good summary of all the available information about ecigs & health when asking are e cigarettes safe:
http://www.bbc.co.uk/programmes/b048034t

The NHS doesn’t recommend ecigs for this prupose, but our perspective is that they definitely can. We all used to smoke, and no longer do so now that we use ecigs.
There have been a few reports of this happening. This seems to be mainly because incorrect chargers have been used to recharge batteries. You should ensure that the correct chargers are always used. The government has issued some advice on this matter:
https://www.gov.uk/government/news/government-acts-to-improve-e-cigarette-safety