I have both a headlight modulator and brake light modulator on my Kawasaki Vulcan 750. I may put them on some other bikes as well. For decades I have been in the habit of just barely touching the front brake lever over and over again to flash the brake lights. That has to be legal anywhere, because nothing has been done to modify the light. You can also modify your turn signals to function as four way flashers, and in my state, those can be used at any speed below 30 mph. So you can flip them on before coming to a stop, and leave them on until you have reached 30 mph. That tends to stop tailgating. I also have a headlight modulator. In the U.S. you cannot have a headlight that turns completely on and off, but you can have one that goes from high beam to low beam several times a second without ever going completely out. I don't know how the cell phone problem is in the UK, but it is a nightmare in the U.S. Drivers using cell phones kill way more people every year than drunk drivers ever did. And yet they are reluctant to pass laws against using them while driving.