Hi Alex
The only entry that sticks out for me in 1881 (also showing in 1891 in same situation) is:
David MacKenzie, 48, Coachman & Public House Keeper, b. Forres, Morayshire - patient at the Edinburgh Insane Asylum in Morningside Edinburgh.
One of the reasons I asked earlier what occupation showed for father David on Alexander's marriage entry....but that came back as farmer so no clues there.
Can't see anything for them on the English census either so not sure where they have ended up between 1871 and 1881

Monica