Sylvia, in case you haven’t already seen the information in the link below, see what you think. It looks as though a descendant of a John Callister b 1846 (who married Louisa Caine), son of a William Callister, has worked backwards on the Callister line and claims that this William was the son, b 1817 Santon, of John Callister / Eleanor Cannell.
If you ignore the fact that this tree probably involves guesswork, and just use it to see what has been included relating to the possible parents of John Collister b circa 1777 and of Eleanor Cannell b circa 1776, there might be something there which proves helpful.
The tree-submitter has suggested that Eleanor Cannell was the daughter of Robert Cannell and Eleanor Hingley, giving children as John b 1773 and Eleanor b 1776, but doesn’t seem to have spotted that Robert Cannell had died before Eleanor’s baptism (noted as posthumous) and that Eleanor nee Hingley/Hinley remarried soon after to William Crellin, going on to have several more children.
The parents suggested for John Collister b 1777 are Robert Callister and Mary Watterson with Rushen as birth parish. I can’t see any evidence for this though.