just found this on Gatwick airport guide, most have been covered but could be useful.
Gatwick Airport Smoking e-cigarettes is not permitted anywhere inside both North and South Terminals. Designated smoking areas are clearly marked outside both terminals.
Heathrow Airport Prohibited use of e-cigarettes inside the terminal buildings. There are dedicated areas for smoking/vaping outside the terminal buildings.
Stansted Airport Use of e-cigarettes has not been permitted indoors since August 2014.
Exeter Airport Using e-cigarettes is not permitted inside the terminal.
Belfast International Airport E-cigarettes can only be used in the designated smoking areas outside the terminal.
George Best Belfast City Airport E-cigarettes prohibited inside the terminal building – use outside smoking areas.
Birmingham Airport Treated in the same way as regular cigarettes in the terminal, meaning they can only be smoked in the outside smoking facility.
Bristol Airport E-cigarettes can only be used in the designated smoking areas.
Cardiff Airport No use of electronic cigarettes is permitted inside the terminal. They can only be used in the designated smoking areas outside the terminal next to Gate 2.
East Midlands Airport Use of e-cigarettes has not been permitted inside the terminal since August 2014.
Humberside Airport E-cigarettes cannot be used within the terminal or outside the terminal entrance. They can only be used in the smoking area.
Liverpool John Lennon Airport E-cigarettes can only be used in the outdoor smoking areas.
London City Airport E-cigarettes cannot be used in the terminal or once you pass through security.
Luton Airport E-cigarettes cannot be used anywhere apart from the smoking area outside the terminal, located outside the front entrance.
Manchester Airport No use of e-cigarettes allowed inside the terminal.
Newcastle Airport Use of e-cigarettes only permitted in smoking shelters at the front of the terminal building and in two more designated areas after passing through security.
Southampton Airport Use of e-cigarettes is not permitted inside the terminal building or while walking to or from the airplanes. They can only be used outside of the terminal building and before passing security.
Other Airports Edinburgh, Aberdeen, Durham Tees Valley, Glasgow Prestwick, Leeds and Robin Hood airports do not provide any information about their policies regarding e-cigarettes
