Hi Kay,
Just had a thought about wills for Thomas. On Brian's burial index there are 7 entries for Thomas Corris between 1795 (when Ann was baptised) and 1841 (he is not in the census):
[Parish - Year]
Patrick - 1813
Braddan - 1819
German - 1819
German - 1831
Patrick - 1832 (age 73)
Malew - 1832
Patrick - 1833 (age 73)
Looking at the Wills index two seem to match:
German - 1820 - Ref: E/2/0106421
Patrick - 1833 - Ref: E/2/0106433
I think the second one looks good as it matches with one of the 1832/33 burials and would place Thomas as born about 1759/60 which would line up nicely with him marrying in 1782. It might be that neither of them is for "our" Thomas but might be worth exploring.
I can't get to the LDS anytime soon, but thought if you were spending time there anyway you might want to look at the Wills. If one of them is "our" Thomas it should provide confirmation of at least some of the children and might even mention a sibling or other relation of Thomas that might help narrow down the search for his parents. It would also be interesting to know if wife Margaret dies before or after him so we could chase up her burial (will?) info. If the 1833 will was "our" Thomas it would probably indicate he is son of Pat Corris christened 28 Sep 1759.
Can I ask which child of Thomas's you are working from? And if you have descendancy data in some kind of shareable form?
Cheers,
Ruth
Canberra, Australia