I know he was alive in 1933 and his children were married by then. I've looked at every likely death in Lanarkshire after that without success and hoped he might have been buried back near his old home and be on a tombstone. I'll try North Lanarkshire burial adminstration to see if I can find his wife's grave and that might narrow the search.
Thanks for all the help and advice. If I find him it'll be one more off the very long list!