Hi Rinder,
My Gt5 grandfather was George Halliday who married Elizabeth Tait. My Gt4 grandmother was their daughter Margaret Halliday 1786-1866. I have found her brothers and sisters, and they almost certainly all moved to Bute in the late 1790s. I don't know why, but I've even found George Halliday 1754-1841ish in the 1841 census on Bute, married to his second wife, Mary Baxter.
I would love to trace George back further. His parents James Halliday and Elizabeth Laurie seem to have been married in Edinburgh, but this doesn't really make sense as they then had children in Berwickshire. Any help, from anyone.
Regards
Douglas in Glasgow