Hi,
my 3rd great grandmother was Louisa Ockenden (1823-1873) who married into the Hymas family in Rayleigh from where I descend (John Hymas 1816-1882ish). She was the eldest daughter of Joseph/Ruth, and would be the brother to your John.
I've got some info on the Ockendon line from the census and have seem some refs to Ackindon to make things more complicated!
I've only just found out the Garpin name tie-in - I see that there are deaths of Robert and Elizabeth Garpin registered in the 1842/43 BMD index for Maldon which would fit well - have you seen them - parents or brother/sister? I also note a few refs to Garpen, though does seem to be a relatively unusual name.
I'd be interested in anything going back down this line, regards, Jon.