Just to get things straight, James Chapman & Janet Kerr proclaimed their banns and married on 28 May 1780 in Dalmeny having proclaimed their banns in St Cuthberts on 26 May 1780. The Dalmeny record has been misindexed in
ScotlandsPeople as 1779 - the original record is clear; the St Cuthberts record is correct.
Agnes Chapman marr Thomas Shatton on 30 Nov 1802 in Abercorn. The surname genuinely evolved in his lifetime to Chattie with an occasional foray into Chatto, then sometimes onward to Chatham (as in my case) and Chattam.
The other thing of note is that Janet Kerr was actually baptised Janet Carre - she was baptised 25 May 1748 Kirkliston to John Carre & Janet Comb. However his continued use of the (unusual) Carre surname was for a relatively limited time while John Carre & Janet Comb lived in Kirkliston where he was the miller (in an unnamed mill right opposite the Carre estate of Todshaugh), clearly influenced by the Carres of Cavers (who themselves were originally Ker but took on Carre - the explanation is in
The Annals Of A Border Club (The Jedforest). 1899, pages 297-305 *). Local records prior to Cavers coming upon the scene are for Ker, Kerr or Keir and never for Carre, Carr, etc, but Richard Carr, who is likely to be Janet Kerr's uncle, seems to have stuck with Carr (mostly!).
It doesn't help my sanity that I have another direct line back to Carr, this time in Bradford West Yorkshire. At least they always stuck to Carr.
*
https://ia802708.us.archive.org/7/items/annalsabordercl00tancgoog/annalsabordercl00tancgoog.pdf