Hi John,
Ive just seen your post, so I checked the 1841 census for Mochrum and found;
Village of Kirk of Mochrum
William Hartley 40 merchant born Wig
Helen Hartley 30 "
Agnes Hartley 13 "
Joseph Hartley 25 "
James Hartley 15 "
Peter Hartley 10 "
I don't know if you already have this info now, but William's father is James Hartley and mother Margaret Thomson, James and Peter's parents are James Hartley and Margaret Christie, I have other info if you want it. Is this the right family?
Regards
Jeanne