Woah.....that's a BIG series of questions.
As a fellow Brit, I can only comment from my understanding of the law - which I think is is the same as yours. I'd clarify it slightly in that "public place" doesn't include railway stations, airports, public galleries. Even though we might initially regard them as "public" they are usually owned privately and the owners may impose restrictions on whether we might be allowed to photograph (and how we might be allowed to photograph - no flash, etc). Stood on a public pavement, however, I understand that we can photograph anything and anyone, even though it / they might be in / on a privately-owned property.
I'm not street photographer or, at least I don't regard myself as one, even though I enjoy snapping away at anything that interests me. And that's the distinction ......"anything that interests me".
I don't do it for a living, or I might find myself applying a different approach; I'm not really sure. Equally, I don't differentiate between whether the person is rich / poor, well-dressed / shabby, drunk / sober, etc. That said, I really don't like what I've heard referred to "poverty porn". That, for me is exploitative and demeaning to the individual. If the photograph is used to tell a story which will raise awareness and, possibly, lead to someone actually doing something about the individual's plight, I'm less concerned. It's a fine line and a complex issue but "intent" is a major factor in whether I'd regard it as acceptable. All of that said, if the individual being photographed isn't happy to be photographed, I would respect their wishes and move on. I've done it several times, here and abroad. I think Peter makes a good point about not adding to a person's woes by making their situation more difficult to bear.
As for spotting the most beautiful women, in my limited experience, most tend not to aggregate around Bond Street. The ones that do, tend to be "trophies" of the rich and vulgar rich. Unless one wants to document the tangerine-skinned and botoxed poodle-carriers of this world, there are many better places to frequent.
A couple of years ago, I was sat having a sandwich in Green Park when a guy with a camera caught my eye. He was far enough away for me not to be able to see what camera he was using but, whatever it was, it had a 300mm or 400mm lens on the front. He was being very careful to use trees, etc, to disguise his covert snap-shooting of women in the vicinity. His victims were varied and I assumed, as a result, he wasn't a private detective or paparazzi. The point of this anecdote is that I believe if one is going to photograph people, doing it covertly isn't really on and it could even get nasty if spotted and someone calls the authorities (whether the photographer was within their rights or not).
At the other end of the scale is the like of Bruce Gilden. I'm not a great fan of the work of his I've seen but he is at least honest enough not to make any bones about the fact he's taking your photo. I don't know but I suspect he might have had a few run-ins with those affronted by his methods. I do know that I wouldn't appreciate his attentions and wouldn't hesitate for a second to swat him.
For me, the subject's station in life / garb isn't the attraction, it's the situation, the light, the shadow and whether the photo will hold my attention for more than a few seconds once it's processed. Proper street photographers might disagree and I have no issue with that but that's why I'm probably ,ore of a documentary photographer than hard-core "street".