Hi Claire,
On BMD there is a marriage record for:
Bridget HARTEN and Matthew McCormac in 1853 Dec qtr. Sheffield.
On GRO the mother's maiden name given for the birth of Ellen McCormick in 1855 was HARTAN
On this site there is a marriage record for:
Matthew McCormick ( parents Math & Ellen) and
Margaret Hartman (parents: Gow & Ellen)
marriage took place on November 5th, 1853 at St. Marie's R.C. Church Sheffield.