Its a law that is unenforceable, the police can't even scratch the surface. People need to apply common sense and I happen to think that more TV and media advertising is the way to go - it worked in the eighties and nineties changing the culture surrounding drink driving and the same could...
If you are in a long traffic jam and have been stationary for some time then I don't have a problem if people use their phones sensibly, i.e. a quick text or call to inform a friend / family of your delay.
Similarly, I don't have a problem if the lights have just turned red and someone quickly...