Hi,
First of all, have you considered that
a) the couple may have had an early son they called John who married a Jane and started having children in 1718?
or
b) that Jane may have died in or soon after 1703 and that John remarried to another Jane?
Secondly, have you posted on the Middlesex Board? Places like Uxbridge, West Drayton, Cowley, Hillingdon are all only a couple of miles over the county border from Langley Marish.
Jill