Mark and medpat,
This is getting quite exciting! but I'm reining myself in so as not to be too disappointed when it doesn't pan out!!
The 1804 Independent, Highfield baptism is certainly looking plausible. The mother's name is also plausible (though I know naming patterns were starting to die out by this time). Thomas and Bathsheba had all daughters (another reason its been so hard to find a possible father for her - I'd imagined a biblical name!): their first was Mary (name of Thomas's mother) but their second (died in infancy) and fourth were Sarah and then Sarah Ann (the latter was my 2xgreat grandmother). I tend to think that, if they've used a forename twice following an infant's death, then that name is usually a parental or at least family name).
I find it strange that the second unnamed baptism you mention, medpat, doesn't even identify the baby's gender!! Did they not bother to look!!
As for wills, I have ordered quite a few Boothroyd wills from the Borthwick over the years but never struck lucky. I'd forgotten I even have Rev Benjamin's will of 1836 - children mentioned but no Bathsheba. I have wills for Richard, Joseph, Michael etc etc but, of the John Boothroyds, I have:
1831 farmer of Quarmby cum Lindley, Huddersfield - names children but no Bathsheba
1839 innkeeper of Holmfirth - names wife Nancy and children, but no Bathsheba. (looks to be the last one on your list, Mark)
1832 fancy manufacturer of Honley - names wife Martha, sons George and Beniah and mentions daughters but doesn't name them!
That last one could have been the right one but wife is Martha, not Sarah - unless Sarah died and he remarried? (cue: me looking for said possible death and marriage!)
I tend not to bother getting Admons anymore as they usually don't tell you much at all, but there are occasionally more details than you expect, so perhaps I'll go for it. It would be worth it to break down this brickwall which has stood solidly for over a decade.
Thanks!