Specifically, what places were most associated with housing the capital's elite? Was there a significant divide between housing for traditionally noble families and the equivalent of nouveau riche? How strictly was separation between these neighbourhoods and lower class areas enforced?
You want to look at Charles Booth's Map of London - see here https://booth.lse.ac.uk/map/14/-0.1174/51.5064/100/0 He was most interested in mapping poverty, but the top category (Upper and middle classes. Wealthy) is clearly clustered around the Hyde Park area.