Yes, Charlie, I am indeed in the US, so sadly will be no help at all getting to those documents not available online. I fear I'll likely be a bit of a disappointment as far as contributing to what you already know. You were far ahead of me when I first came across this thread and still are. I found the magazine obit for John Jones B1731 and the book describing his grave marker, so thanks for those in addition to my thanks for your answers to my questions. Your grave marker pictures were already unavailable, so I was glad you had transcribed the information from them.
I have not come across Jane Jones Browne B1793. For me, being another Jane and the age of Jane Barker Jones at her birth argue against her being a sister to my Jane, but not to the point I'd say it's impossible. I wonder if she may be in the next generation. Do you think the John Jones and Jane Barker who married in 1769 are "ours"? If so, that leaves a lot of room for yet-to-be-discovered (by me, anyway) aunts and uncles, perhaps even a previous marriage. Maybe she's the daughter of an older son of John Jones B1731?
I had wondered if Shepherd might turn up as a surname farther back. Interesting that you found a connected Shepherd! Not, as yet genealogically connected, though? Is the place where Joneses are living called "Eagle Hill" in the tithe records and in some deeds, I think, the same place called "Woodside" elsewhere? If not, can you explain the distinction better than what I've been able to figure out on my own? Rachel Barker Marks being a sister to Jane Barker Jones and Joseph their father was my interpretation, too. I don't think I've seen documents to which Rachel was a witness, and the only one I saw witnessed by Thomas Condell was the one I referenced that connected him to the Joneses and Barkers. I do recall seeing Thomas Barker's name, but I don't think I'd worked out how he was connected when I had to make myself stop because I was acting too obsessed to do anything else.
I grew up near where Jane's grandson lived and his property is still in our family. I love that I have pictures of people separated by five generations in what is recognizably the same front yard, but your Newtown Saunders roots are more impressive!
If you are adding Jane to your tree, you would probably like to have some of the source documentation I have for her. I'll try to PM you a bit more, but a marriage record is available online here:
https://www.familysearch.org/ark:/61903/1:1:WG49-G13Zand the ship's passenger list when she and her children emigrated here:
https://www.familysearch.org/ark:/61903/1:1:K8C9-ZWBAs I mentioned, she had an additional daughter who also emigrated: Elizabeth B1805. The older girls' ages are a bit off on the passenger list. (I wonder if something was easier if they were all under 21?) Other documents indicate daughter Jane was born 1802 and Sarah in 1803. I have traced all the children to their deaths in the US, so they were out of the mix in Ireland after 1824. The only one for whom I have nothing explicitly stating a relationship is Joseph, but dates, places, business connections, etc. make me fairly confident he was Joseph Dodd Condell, so I would be alert to any Dodds who seemed connected. If that ever turns up, it could be on the Condell side, though.