I've also found several pages that claim Hamilton went on to work for the post office in the area. Apparently he also only liked to sing people a verse or two of his songs at a time:

Learned over a period of years, a verse at a time, from Geordie Hamilton -- a man who tantalizes other singer by singing them a verse or two of a gem, then saying, "Ah, you don't really want to hear that", and singing something else. A song learned from Geordie is a testimony to patience, a great man and a giant of a singer. (source)

The book Fuzz to Folk by Dr. Ian Green wrote that his repertoire of songs ran "into the hundreds" (link). He was also a regular patron of the pub Sandy Bells.

As an aside, searches for Geordie Hamilton seem to be cluttered with a character from some book called Island of Sheep by John Buchan; if you don't know it, a handy searching trick is to put a minus sign at the end of your search phrase for anything you don't want to see results related to. So for example, my search was "geordie hamilton" scotland -buchan -"island of sheep"