Thanks for your message. I don't know if you are aware of this, but the Family Search site of Latter Day Saints takes the Metherell family back to at least 1675.
A few years ago I visited the cemetery in Little Britain, Ontario, and wrote information from the markers. I still haven't put together how some of the Metherells (Samuel for instance) fit into the family, but my mother has a death notice of his.
If you would like to contact me directly, my email is firstname.lastname@example.org.