Templar75
Thank you Archie for the info regarding the Mill. It is definitely down as Brustain in the Tranent parish marriage register so someone couldn't spell it correctly. I'm wondering if Isabella's father didn't attend and she just gave his surname! Isabella Gavine was resident as a servant at Dunse Castle on marriage but in 1841 I found her as Isabell Gavien. I wish I could find her father in 1841, I wonder if he actually lived at the Mill. I will try again giving the correct mill spelling.
I do have the set of censuses you gave me, but thank you for the extra little bits of info regarding the children, it colours it doesn't it.
I got David and Margaret from the IGI - David b abt 27 Nov 1851 ch 14 Dec; Margaret b abt 29 Nov 1851 ch 30 Dec but they must be twins surely. Margaret, as you say, had disappeared by 1891 after father William had presumably died, maybe she got married at last !!
I shall hopefully print out the map you gave me when I've renewed my inks !!

Poppy10