Brake lights come on when car is off!?

[Calluma3]

Hi guys just a quick one, my brake lights decide to come on when my car is off and most of the time they come on in the middle of the night and they are draining my battery I heard it could be the brake light switch but I'm unsure... Could somebody point me in the right direction please as I'm a bit confused thanks

 

[Granta]

Scan it for codes first. Brake light switch can throw up a code.