My Ketleys went from Gt Saling to Gt Leighs, which is none to far from Gt Waltham, not sure if the following info will provide any clues but just in case here goes
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Anthony Ketley born around 1708/10 was baptised at the age of 28 in Gt Saling so of course no parents names were given, he married Mary Pasfield in 1733 at Felsted, the marriage entry recorded that they were both "of Old Saling", the Gt Saling marriage register noted that they were married in Felsted.
The IGI claims Anthony was born 1710 the son of Richard Ketley and Elizabeth Farrow (no other details were given), which could be correct as Anthony named his first child Richard (born 1734) but I did not find a daughter named Elizabeth. From my own research, Richard Ketley & Elizabeth Farrow married 1707 in Lt Leighs but a search 1706 to the end of 1721 did not reveal any baptisms for their children there.
Richard 1734 married Martha Loane in 1765 in Gt Leighs and all their known children were baptised in Gt Leighs, the generation after them were also all baptised in Gt Leighs.
What Ketley births/marriages are you looking for? I have some "spares" in the time frame you mention from various Essex PRs that I've collected whilst searching for my lot.
Regards.