Vaping, Electronic cigarettes

From Gatwick's website

"e-Cigarettes must be taken through security and can only be stored in your carry-on baggage, they are strictly prohibited in checked (hold) baggage. This applies for both domestic and international flights.
As long as you stick to the general rules about what is and is not permitted to take through security, you should not encounter any difficulties. The only issue that you may have is when it comes to the e-liquid because you can only carry containers no larger than 100 ml through security. You will also have to place any e-liquid inside a clear plastic bag like any other liquids."