UK rules on the use of e-cigarettes at airports and on airplanes.

Rules for carrying electronic cigarettes on airplanes

Carrying electronic cigarettes: On flights in the United Kingdom, you can bring electronic cigarettes and disposable electronic cigarettes on the airplane, but they must be put in hand luggage or carry-on, and must not be put into the checked baggage. The reason for this is that e-cigarettes contain lithium batteries which are a potential fire risk.
Packing of spare batteries: All spare batteries must be packed separately and placed in hand luggage to prevent short circuit. If you are carrying disposable e-cigarettes, it is recommended to put them in a transparent plastic bag and carry them in your hand luggage.

Carrying e-cigarette liquids

Carrying limit: You can carry e-cigarette liquids in hand baggage, but you must follow the general rules for carrying liquids by air, i.e., all liquids must be packed in containers of no more than 100ml and put in a 20cm x 20cm transparent re-sealable plastic bag.
Check-in rules: If you need to carry more than 100ml of e-cigarette liquids, they must be placed in your check-in baggage and it is recommended that you use a sealed plastic bag to prevent leakage.
Regulations on the use of e-cigarettes in airports and airplanes
No smoking in airports: The use of e-cigarettes is strictly prohibited in all UK airports. However, most airports provide designated outdoor smoking areas where you can use e-cigarettes.
No smoking on airplanes: the use of e-cigarettes is strictly prohibited on airplanes. It is recommended that you store your e-cigarette device in your hand luggage to minimize the urge to use it.