Hi David...I have a John Mossop of the right age in my tree...but don't think that I have any further details to offer you.
I have the same siblings listed as you with the father as Lewis and Elizabeth as mother from the 1881 census.
I believe that Lewis was the brother of my husband's great-grandmother Elizabeth Ann Mossop who married Thomas Haworth (sometimes listed as Howarth) in Blackburn in January 1874.They too had a son John Haworth born in 1877 in Preston.He later married Lilian Bennett and they emigrated to Vancouver Canada in 1910 or so.This would make your John and my John cousins I think...
I have other siblings of Lewis and Elizabeth Ann as Clement, John Albert, James A. and the parents were John Mossop and Elizabeth...who were 59 and 60 in the 1881 census.All children seemed to be born in Ramsbottom, Lancashire...and the clue for me was that they later lived in Hollin Bank House in Blackburn where John Sr. was a Cotton Mill Manager.
Hope this helps...perhaps we can connect to fill in the details of when where others emigrated to. Please reply or e-mail. Sandi