I think attitudes changed with regard to drink driving, are changing with regard to speeding, and crucially have changed out of sight in those parts of London where cyclists predominate. I'm suggesting that while individuals vary, the body politic of driving is moving with the times and can be moved further.
As for the traffic police/speed camera dichotomy - I'm not at all impressed by the press campaigns and people like Safespeed. In the end people don't like being caught, and are, in the main, prepared to modify their behaviour to reduce the chances of being caught. The irony is that while helmet cams rightly report on bad behaviour in London, the respect shown to cyclists has increased dramatically, with buses leading the way, but private cars following on close behind. I say irony, because, actually, all political movements tend to flourish when events are already going their way (see Russian revolution and rise in industrial wages prior etc., etc., etc.....). My cause and effect thing above was a bit simplistic - cause and effect are intermingled, with greater confidence within the body politic of cycling leading to greater expectations and assertiveness, which, in turn, results in better driver behaviour.
Put another way - nothing has ever been gained for cycling, or any other cause, by just hoping for it. People like Maggers and BM are engendering a hesitation within the body politic of driving, and that hesitation is compounded by the rise in the number of cyclists in my part of the world. Whether BRSU is ploughing a lonely furrow in Swindon is, perhaps, beside the point. Quite apart from nobody caring about Swindon, the town, 'blessed' with a zillion cycle paths is not enjoying the cycling revolution (I put it no less strongly than that) that is happening in London. Swindon's drivers have no real need to think (the council having switched off its Gatsos) and will continue to exhibit the untermensch behaviour that BRSU records.
So helmet cameras are part of a shift of attitude that is binary. We gain in confidence and our expectations rise on the back of that confidence. Motorists lose the sense of impunity they've enjoyed hitherto. It's patchwork, it's partial, but that's the nature of things. Overall I remain both optimistic in general, and gain some of that optimism from Maggers' and BM's efforts.