There was only one Liggett/Leggett of any spelling in Carnteel parish in the Tithes, but 3 in Aghaloo parish and 4 in Clogher parish.
See Tithe indexes to each parish on this very helpful County Tyrone web site, which includes PRONI source references (PRONI file numbers & microfilm numbers):
https://cotyroneireland.com/tithe/Tithe Applotment Book Indexes
Aghaloo Parish, County Tyrone, Northern Ireland 1825
George LEGGATE - Tullyblitty
George LEYGETTE - Cumber
George LEYGETTE - Cumber
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Carnteel Parish, 1827
Nathaniel LIGGIT - Knocknarney
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Clogher parish, 1829
Andrew LIGGIT - Cornamucklagh
John LIGGIT - Lislee
Joseph LIGGIT - Tychany
Samuel LIGGIT - Corboe
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Errigal Keerogue Parish, 1832
Andrew LIGGET - Keady
James LIGGET - Keady
Joseph LIGGET - Keady
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A brief index to Griffith's Valuation is here:
Griffiths Valuation of Ireland
https://www.failteromhat.com/post1845.phpAnd details and maps of each parish, townland, and occupiers are listed here:
https://www.askaboutireland.ie/griffith-valuationThere you can read details for:
James Leggett - Derrycreevy townland, Carnteel parish, Co. Tyrone
James Leggett - Keady townland, Errigal Keerogue parish, Co. Tyrone
Elizabeth Leggett - Keady townland, Errigal Keerogue parish, Co. Tyrone
Keep in mind that "Liggett" is spelled many different ways, often phonetically and not by any spelling standards like we use today. I'd highly recommend looking in all the "L" surnames in on-line indexes for variations.
Microfilmed church records at PRONI are extensive, including several of the Presbyterian congregations you've mentioned. I do suggest researching them THOROUGHLY for references to Liggetts. Aughnacloy, Ballygawley, Minterburn, and so on.
And, don't rely too strongly on what someone "told" you about this ancestor or that ancestor. Search for the records and proofs. For instance, on the lady (married to a Liggett) telling you that "Margaret Robinson" was the wife of Joseph Liggett and the couple married in 1816, what age was this informant lady when she talked with you, when did she relate this fact to you (such as last month, or 10 years ago?), where in Co. Tyrone had she lived, and how was she in a position to know about the Liggetts? Obviously she was telling you about her husband's family -- so who told HER what she was telling YOU? She wasn't born knowing anything about the Liggetts! Did her husband's mother or father tell her, or one of her husband's cousins told her? Had she researched her husband's family? How was he descended (assuming that he WAS descended) from Joseph Liggett and Margaret Robinson?
I haven't been back to Ireland and visited the "new" PRONI building, but friends and relatives report that it's wonderful.
Annie