I was born in Pretoria in 1939. I am sorry to say that I have only today seen this correspondence, but I do have something to add to it. My mother was Afrikaans-speaking until 19 years of age, and my grandfather, though having the surname Mills, fought for the Boers in the Boer War, and spent two years in Ceylon (Sri Lanka) as a POW, and, I am told, narrowly escaped being executed as a supposed traitor.

The version of the song I learned as a child had three languages in a single verse. (There may have been more, but I do not recall them.)

Totsiens, Sarie, totsiens: (Farewell, Sarie, farewell
Alles sal reg kom, en dan, (Everything will come right, and then)
We´ll be marching to Pretoria,
Aikona, sakabona,             (? language, ? meaning?)
We´ll be marching to Pretoria,
Back into your arms again.

As I learned it from predominantly Afrikaans speakers, and the suggestion is that Sarie is living in, or near , Pretoria, it does sound as though THIS version was being sung by Boers, albeit, like my own family, with perhaps some British links.