No idea what you'd be able to get in SA - you are ideally looking for a food with a protein content of around 12-14% and a fibre content as high as possible - preferably at least 18%. A pellet food is better than a mix because buns tend to select bits of a mix and leave other bits, which gives them an unbalanced diet. The pellet foods in the uk are generally pretty tasty and buns look forward to eating them! In the UK the most popular brands are burgess excel (plus excel lite or excel junior/dwarf versions), science selective, allen&page plus a couple of lesser known ones like bunnybasics t.
The largest portion of your buns diet should be hay/grass. A small amount of pellets and some veg are also good, but if you can get a reasonable pellet, you shouldn't need to feed any additional supplements as buns systems are designed for a poor nutritional value diet.