"So all chronology is up for grabs in the area, the way I see it "

It looks like that, not forgetting saxon as well! There's continuity of "significance" in its position, St.Arilda's well is not too far away - she followed the fate of all good nuns who would not yield to the local tyrant, and had her head cut off. Her birthdate is 448 ad, so with roman coins there, you need to excavate below the church to find evidence of prehistoric connections - but I bet its there.....