As far as I can see it should be legal, as long as your plate is on display and on the bumper then it should be legal. I think it comes with it's on keyfob, but I'm going to look at putting a switch in the car and wiring it into the ignition system. So turn on engine; numberplate pops out. Turn off, numberplate retracts. As for size of plate I'm not sure, but I think I will get my plate made up jdm shape so it tales up less space. Should be easy enough to make it take a uk plate.