Many thanks for your reply. I could not find William Buchanan on the 1851 census but I found him on the 1861 living at 25 Portland Street Lanarkshire (Callander Worker)with Purdie family.
I have his MC1863 to Mary Ann Hunt (whose surname should be DUKE but that's another story!!!)
They were both living at 65 South Portland Street.
States his parents James Buchanan (cloth lapper) and Catherine McIntyre
I also have his DC1910 living at 28 Well Street Lanarkshire.
In 1851 there is a William Buchanan (adopted) child.