Hi Duport,
Have been looking at the 'Winchcombe' Jacksons and can't make a definite link.
The August 1698 birth I have found seems to be for Willus Fillius (William, son). Other records name Anne, Joanne, Eleanor, Maria, Edith, Richard and Francis, which are not the pattern of names that were used by the 'Windrush' families, using Victor's records, earlier.
Names like Thomas, Susanna(h), Benjamin, Elizabeth, John and Mary crop up for me (in several generations), which still makes me wonder whether Rowland has a more direct link to Windrush - even though his baptism remains a mystery! I wonder why he was named Rowland?
On a different thought, do you have any other information or ideas about the location of Cockburys or Lammerys? I have found windrush Quarry on an old map and the Grade II Listed Quarry Cottage still stands nearby.
MDean