Wow Smud - your search method looks very different from mine.
Yes ... I was looking at John and Mary Lewin, married in Sarratt on 30 September 1684, and their children.
Their son Matthew was baptized on 18 March 1704, though ... so would have been at least 43 in December 1747. WAS he the Matthew who married Elizabeth Saunders? Or is there another generation in there somewhere??
Either way, I think that the John Timberlake who married Mary Lewin looks like being The John, son of Thomas who was baptized in Ellesborough on 3 February 1655/6
I cannot find his parents' marriage (civil war / Commonwealth) - but their first child is, I think, Thomas son of Thomas baptized in Ellesborough on 10 March 1649/50.
If that is right, then John's father Thomas looks to have started his family very young, as I think HE is the Thomas Timberlake, son of Thomas, baptized in Ellesborough on 26 January 1633/4. THe parents for this baptism are presumably Thomas Timberlake and Ann Kinges who married in Ellesborough (or Edlesborough - the FindMyPast record set has both locations on different records, but it is obviously the same marriage) on 13 August 1632.
This Thomas, in turn, looks like being the Thomas Timberlake, son of John & Elizabeth, who was baptized in Chesham on 24 April 1603.
That's quite a long way back up the tree to get on a Saturday afternoon ... and yes, we have now strayed across the Buckinghamshire border