Your GGF would have applied to have his Anglo-Boere Oorlogs medalje on an application form called Vorm B.
These Vorm B's contain a lot of information, including his service history: who his officers were, which commando he served with, and where he fought. These Vorm B's are stored in the archives in Pretoria, and you can either go and look yourself; or what I do is to pay someone who does this professionally, who will then send me a high-resolution photo of the Vorm B - and any other papers they have. It's usually quite quick, and I recommend Dewald Nel who is: [email protected]
all the best of luck
The past is not dead. In fact, it's not even past.