The Highway Code says that you should:
only use flashing headlights to let other road users know you are there
use flashing headlights when you want to give way to someone
flash your headlights repeatedly if someone dazzles you at night
never flash your headlights
If someone flashes their headlights at you:
They are always giving way
You should ignore the signal
They might be giving way
You should report them to the police for breaching the Highway Code
In the signals lesson, we suggest that when a signal is needed, you should allow your direction indicator to flash at least three times before starting to brake, accelerate or change position.
You will be asked to use arm signals on your driving test if your indicators or brake lights fail.
If a driver behind is following too closely it can sometimes be helpful to:
Give a hand gesture to warn them that they are too close
'Brake check' them with a short hard 'stab' of the brake pedal
Touch the brake pedal gently to activate your brake lights
Put on your hazard warning lights
Hazard warning lights are most often used when a vehicle is stationary. However, you are permitted to use them if you have to slow down rapidly on a motorway.
It is illegal to use front or rear fog lights when:
Driving at night
Visibility is greater than 100 metres
On high-speed roads
Between the hours of 7am and 7pm.