I'd be interested to know what you mean by the posh Catholic churches and indeed which decades you refer to.
Looking at the 1860s and 1870s and 1880s there was a very great difference between parishes how the irish and their aspirations were treated by the church eg in the 1870s an (irish) priest in hoxton ripping down and dancing on a home rule poster, another irish priest in marylebone refusing the use of Catholic school rooms for a meeting to raise funds for relief in Ireland in 1879, while by contrast another irish priest allowed the use of the clerkenwell italian church schoolrooms for the founding meeting of the London irish home rule association. The foundation of the temperance league of the cross by archbishop manning was used by elements of the nationalist irish to promote their own views, eg at a public meeting in peckham the green sashes of the league being adorned with irish nationalist symbols. Archbishop manning also gave a letter of introduction to an irish pavior, so he could gain an interview with the archbishop of Toronto.
From my pov, the way the rc church in England treated the irish varied from place to place and time to time. But yeh I'd be interested to see your source/s