If you are being followed too closely while driving you should?

Increase Your speed

Updated answer,

If for instance you are in a twenty zone and someone is driving to close to rear of your car, you have the right to go slower, if the driver behind you still drives to close hit the brakes a few times, to let him know, you know he is there.

On the motorway if you are adhering to the speed limit, then slow down for a few seconds, and the car behind should pass you.

Sometimes the best thing to do is pull off the road you are on and let the offender go on. I highly advise against hitting your brakes. There are people out there that suffer from road rage and you may end up in an altercation by hitting your brakes.