I apologise but I do not have the time to respond fully to the discussion regarding shishim ribo. But I would advise taking a look at the following summary of issue, which appeared in Ohr Yisroel:
http://hebrewbooks.org/pdfpager.aspx?req=13626&st=&pgnum=230
http://hebrewbooks.org/pdfpager.aspx?req=1418&st=&pgnum=166
There is no evidence that Rav Padwa senior was concerned about a reshus harabbim. I have heard from one of his family members that this was not his concern at all, and one of his sons said as much to the Chernobyler rebbe of Boro Park when he was sitting shiva for his father.
It has been demonstrated elsewhere that the Minchas Yitzchok would have no issue with an eruv in NW London. Anyway, as Dayan Westheim testified in his shiur, the Minchas Yitzchok was only concerned with whether shishim ribo traversed a particular street, and not whether they inhabited the city.