I've seen them, and they're exactly the same style as a similar sticker campaign from England from around 2001 but the sticker said "DON'T BE A DICK!" in big white letters on a black background.
We were stopped once whilst entering Homelands Festival car park by what we thought was a rozzer saying that he needed to search the car. He let us sweat for about 30sec before slapping the "DON'T BE A DICK!" sticker on my mates forehead. Turns out he was just a carpark attendent.
That sticker then spent the rest of its life on my fridge at uni, but I used to see them around different cities.
No idea what BNE is though.