Hoverman: get out of bed the wrong side today, eh? I realised it was Spain fairly early on, but forgot to edit my post....sorry about that, my lord.
If someone holds a PPL surely you must recognise this as atleast the first professional rung on the flying ladder, no? Don't make them out to be stupid, they know a little about helos.
If I was in the vicinity and witnessed a large(ish) helo like the 109, land in amongst some cars in a car park and "felt" it to be 'without due consideration' / 'ignorant of its surroundings' / crass stupidity'....then I would most certainly speak to the driver, as I would any driver of any machine which might cause damage/injury to bypassers due to an irresponsible attitude. You don't need to know the 'rules' to action that.
If the observer witnessing the activity knew a lot more about the rules and felt that these had been infringed, then I would
(a) talk to the driver first - politely, to determine his/her motives, and,
(b) based on their response, leave it there or report them to the aviation authorities - no qualms whatsoever.
We've discussed this 'snitching' episode before so let's not go over it all again.
The rules are the rules...someone breaks them (to the detriment of innocent bypassers)...."book 'em danno"