Are there many Catholics in England?
Per the BBC, "...the Catholic Church claims just over four million members in England and Wales - and another 695,000 in Scotland. Out of a total population of about 60 million, that means about one in 12 people in Great Britain is Catholic."
There are approximately 4 million Catholics in England, but the number of active Catholics is larger than the number of active any-other religious group.
When I went for mass, whether in Brighton or London or York or Bristol, the churches were always full on Sundays and frequently on weekdays.
In contrast the Church of England churches were sadly empty all the time
Baptist Churches and Eastern Orthodox/Coptic Churches were, like Catholic churches, full. I didn't visit any Evangelical/other Christian churches, so cannot comment on them. NOTE: this was before the wave of Eastern European Catholics and Orthodox came to England -- from what I know, the Catholic and Orthodox churches are burgeoning due to these new migrants
Church of England parishes are dying, rapidly. If you are religious, the CoE offers you nothing -- you will either go traditional and become Catholic/Orthodox, or you will join a Baptist/Evangelical church. If you are non-religious, the CoE offers you nothing, not even a social club.