Thanks for your reply. I appreciate your taking the time.
I checked the PRs of Stafford, STS, where Stephen LANGTON and Elizabeth HOLMES were married in 1785 and I did not find a baptism circa 1755-70 for either of them there. Therefore I have no idea where Stephen (and Elizabeth) might have sprung from. There seem to be a lot of LANGTONs in Lancashire, but the only Stephen LANGTON on the current IGI is one baptised in Devon. I'll certainly keep Josiah LANGTON in mind, if I ever find out where Stephen came from!