Most people in the UK will remember when a walk to the pub and suddenly, smoking went on. Since the ban on smoking, those days have passed. However, the advent of e-cigarettes has now complicated matters and resulted in a lot of trouble about whether or not anybody can vape in the pub. As with a lot of questions of this type, there is no clear answer. However, it’s best for you to assume that vaping isn't permitted and to ask the staff if further clarification is required.
At the moment, e-cigs aren't covered by the legislation that bans users from smoking indoors. Now, this is because smoking needs the burning of a substance, and nothing burns in an e-cig when the person is vaping. But, while there are no national laws preventing use, different venues are permitted to apply their rules at their discretion, and many do so - always to the detriment of vapers.
National pub chains Wetherspoons have implemented a ban on vaping in pubs in the UK. The Wetherspoons site explains that: “We don't permit the use of vaporisers or e-cigarettes outside of the areas designated for smoking on our premises. This will include external areas and hotel rooms.”
The Mitchell and Butlers website show a similar note: “For the comfort of our guests, Mitchells and Butlers don't allow the use of e-cigarettes within our premises. Recognising that the fumes are non-harmful and vapours this is not known by everyone and can result in confusion for others. So, to prevent this, we ask that guests don't use e-cigs on our premises.”
Also, vaping seems to be banned at all English Premier League grounds, though how heartily the enforcement of this ban is a different question entirely.
The enclosed spaces which come with any public transport were often going to be a tricky area for vapers. Therefore, vaping is banned on all train systems in the country except for Southeastern and is prohibited in the London underground too. All airports as well as major United Kingdom airlines have a full ban on vaping, even though you're allowed to take the equipment on many planes. Now, Heathrow terminal 4 has a dedicated vaping section for people who are aching to puff on their favourite vaping liquid.
Enterprise is a leased as well as a tenanted pub company that means their venues are given to personal operators. It's these operators who operate every part of the venue, instead of Enterprise, and ao decisions like use or non-use of electric cigarettes are left to those people. It implies that while an Enterprise pub may permit vaping, another may not.
The best thing is to ask any staff at the establishment – and that also applies for any pub which does not have any clear rule. Where vaping in some public places are concerned, it is best to play it safe and have confirmation before you use your device.
Finally, your place of business is your premises, and you have the right of withdrawing your permission for some to enter the premises given it's on non-discriminatory grounds. But, if they refuse to leave or try to access, they commit a trespass.