The only time I've seen the kind of behaviour the OP described, it was also Australian acrobats (in the High Street during the Edinburgh Festival).

Maybe it was the same people. Any comments from the Australians here?

This type of approach is relatively recent here I think, within the last five years or so I guess. I have seen it here, maybe the same act, but didn't think it was overly aggressive, more a case of being over egotistical and "bad manners". Where it was once "pay me what you think I'm worth" it's become "I AM worth at least $xxx but you can give me more".

Only once do I recall being totally turned off by an aggressive approach. It was three or four years ago in Cambridge, in a square near The Corn Exchange. The performer was North American (can't remember if US or Canadian) and was demanding a minimum of ₤25, lecturing at length on how it was the "right" thing for the audience to do. Can't remember what the act was - nothing memorable about it.