Gasp!
Hello Trish, and thanks very much for your welcome and response too.
This is really helpful information, I'm very grateful to you. It also explains why Mary JONES appears in that other person's Tree. Furthermore, it indicates a clear error in that Tree, about a different surname which has stumped me until now. (Incidentally, you and Queenie may find it reassuring to know that I don't uncritically accept info from other people's Trees until after I've cross-checked it several ways, as best I can, and there's certainly been lots of information which I've elected not to accept. Nonetheless, your advice is much appreciated).
It's also good to see the place/parish names of St Woolos and St Mary, Nash, in your information, as these appear in my Tree as the origins of those Monmouthshire LEWISES (and/or subsequent spouses) who re-settled in Whitchurch, Glamorganshire. Indeed, Edmund1743 was the farmer of Deri Farm, Rhiwbina, Whitchurch, and this passed down to his son Edmund1774 and then grandson Edmund1797. I haven't looked into the title of the land yet, but my working assumption is that they were tenants rather than freeholders, and that the land was probably part of the Tredegar Estate. Similarly, other grandsons (from William1807 onwards) were Innkeepers of the Holly Bush Inn, Whitchurch, which I assume was also part of the Estate.
Incidentally, William1807 became connected with the Holly Bush Inn sometime after his marriage (1831) to Jane JONES, whose father Joseph had been Innkeeper there for some considerable time. It's tempting to hypothesise a connection there with the earlier Mary JONES, but my layperson's understanding is that there was more than one JONES in south Wales at that time...
Best wishes,
Jeff
PS thanks also for the recommendation about FreeREG. I do use that, but I'm not certain that I know how to get the best out of it at this stage. However, I'll continue to blunder on enthusiastically, in the hope that I'll get better as I go along