Hi Jack,
I am related to the Hasletts and the Murrells who were connected to the Shannons of Limavady. The following is from some research by The Rev Dr. T.H. Mullen, a Presbyterian Minister who was brought up in Limavady. Info in brackets is my input. I hope it helps.
" SHANNON. William Shannon had a hearth in Derrybeg in the 1660s (info probably taken from the Hearth Tax Rolls of 1666). In 1692 George Phillips (primary landowner of the Limavady estate) leased half of Derrybeg ( an area just NE of Limavady) to John Shannon at £8 per year and three couples of fat hens every Xmas, the land to be enclosed and fenced off. John Shannon conveyed the lands to his son James in 1720 and he in turn devised them by will to his son James who in turn devised half his lands to his son William in in 1818. The farm eventually came down to Douglas Shannon who sold it to ian Grant. William Shannon, formally of Derrybeg, died in Philadelphia on 29 July 1852. James Kelly Shannon of Cambusdoon, S. Australia, second son of the late D. Shannon Yatara, formally of Derrybeg, married Christina Scottof Paddy's Plains in 1881. H. M. Shannon opened a draper business in Ballymena (Co. Antrim) called the Emporium about 1853. Family is related by marriage to Moodys of Coleraine, Hopkins of Bolea, Hasletts and Murrells." ( info was taken from various douments in the Public Record Office Northern Ireland PRONI.)
Regards