Thanks to the Annan FHS, I've found this entry in the Annan Old Church Kirk Session Minute Book, record dated 26 Apr 1850:
"Agnes Kinnear: Res. with husband William Roddick, Merkland, Kirkpatrick Fleming. Previously res. with mother at Dumbretton. Has two children aged 8 and 5 still unbaptized. Minister of KPF to rule on discipline an restoration of privileges.
Fathers: Wm Heughan (sic.) of Bewcastle and Robert Carruthers."
There are only the two William Heughan (Haughan) in the 1841 census and the father was presumably running out of steam in that department, dying after a very (re)productive life in 1848. So, I assume Wm was a chip off the ol' block at the age of 21 and just a year before his own marriage to Margaret Johnston at Gretna Green.
In the 1851 Scottish census, Wm and Agnes are shown living in Kirkpatrick Fleming. The two oldest children are both born Annan 1842 and 1844, respectively Elizabeth and Margaret (both surnames recorded as Roddick). Subsequent children are born Kirkpatrick Fleming. There is a four year gap between Margaret and the next Roddick child.
Elizabeth went on to marry John Law in Longtown in 1860.
All this is new to me but if anyone has any further info I would love to hear from them.
Rgds, Sue Barnes