I have looked at the various documents and found that I had John McLeod STEWART down as being a 1820 DOB in the Musselburgh area. However, from the census it would seem he was 8yrs older than Alice FAIRBROTHER giving them DOB of 1812 and 1820 respectively. Also John McLeod STEWART's place of birth is Aberdeenshire.
I have a few John STEWART born in 1812 in the Aberdeen area however no record of middle names which is proving to be a bit of a pain. Likewise, for Alice FAIRBROTHER I can not find a record of any birth (in UK or Ireland) or marriage to John STEWART. Will keep looking though...for the time being.