I haven't come across any Stopporton's in my Corkill tree, and my Mary Ann doesn't fit (married Philip Cain). I do have a listing for a Mary A. Corkill, b. 1864, St. Luke's, Baldwin, although this doesn't seem likely given the dates you've provided above. Of my other two Marys, only one is unaccounted for (b. 4 Oct 1815) and is much too old for the 1887 date. If I do come across any Stopporton's I'll be sure to contact you! (If you'd like to view my Corkill tree, it can be found on www.manxtree.homestead.com/main.html)
Cheers,
Melodie