I am a decendant of Leyson Hopkin Davy (and therefore Jonathan). My father is William Humphrey Davy and his father was Walter Humphrey Davy.
My aunt, Joan Coburn (nee Davy) put together a family history which has a few glaring errors however is a great basis for family research.
I'm curently in the UK and heading to Cardiff in September to track down some of the old family stamping grunds - Angel St where Jonathan was a grocer, the farm in Glamorgan, births, death & marriages...only have a couple of days but ... !