Queenie, that is very kind of you, thank you. Lots more for me to look at there over the weekend to tie in all the families.
I've also found more information which I think adds weight to Mary Lester being John's daughter, which I will note here incase of interest to you or anyone else in the future doing a search!
John Exton and Hannah Lester had a son, Thomas Exton (b 1771). who would have been Mary's nephew.
In Thomas Exton's will he mentions Charles Campbell Morris (Mary's Grandson via Campbell Morris, b 1770), and Mary Ann Saffery (Mary's daughter, b 1774).