Hello Sue,
I am aware of Castle Douglas. Later censuses for Elizabeth Wood consistently name Isle of Man. Only one specifically mentions Douglas in Isle of Man. I know Elizabeth Wood marries John McDonald (yes!) in Kinghorne, Fife on May 11, 1868 because on all of their children's birth certificates (5) that marriage date is written down. Even though I can't find the actual certificate. I know Elizabeth Woods parents from her death cert. in 1927. I also know that John McDonald is from Ayrshire. So somehow they got around!
Thanks,
Colin