Rory,
I'd not seen those advertisements for the sale of the property in 1912 and then subsequently in 1020 and 1925. The 1912 sale refers to the land as owned by Patrick McAlister deceased and in the possession of Eneas who was recently deceased. In the 1901 and 1911 Census Eneas and his two sisters are elderly and apparently unmarried. Patrick (1818-1903) is probably his uncle who had four daughters and one son (who may not have survived) so the land might well have gone to his nephew.
I think that John McAlister (1785-1866) and Catherine McLaine (1793-1855) who are buried at Glenravel are the 1st cousins of my Patrick's grandfather John McAlister (1790-) and Jane O'Neill (1790-) - that's the theory anyway. I'd like to try to identify the exact location of the Irish Omerbane land and the NLI have a wonderful tool for overlaying the 1841 maps on the modern map - not sure if that also works for Antrim but will check.
My great grandfather was worked on the land (wheat growing, orchards and timber) so he's not likely to have majored in classics! I think that Patrick McAlister was born in Co Down and became Bishop of Belfast. My great-grandfather learned thge hard way that you can't make a living from growing wheat on the 100 acres that he received as a grant. Even at that time, the minimum was several hundred acres and now is it more like 6,000.
Many thanks again and I'd be glad of anything else that you find.