Hi Karen, Welcome to Rootschat

On a modern OS map Gled Hillock is marked as being 500m from Brambleburn Farm on the South East side of Lurg Hill.
It is marked on this map if you zoom right in to the black and white version. It looks as though Alexander Morrison only moved to the next farm building over.
http://geo.nls.uk/os6inch/google.htmlLook for Edingight House and you should find it.
I see he is listed as Alexander Morison (with one R) at Bramble Burn in the 1841 census (FreeCen), but in 1851 it's Morrison again.

There is a possible death for him on Scotland's People.
Using soundex on surname, and "Alex", with birth year 1807+/-5 years there are 2 deaths in Banffshire.
1 of them is in Grange in 1873 which would explain why you couldn't find him in later census records.
It might be worth viewing the image to see if it lists him as widower of Ann Lobban. His son James may have registered the death.
Hope this helps
Kirsty