Yeah, it looks like you guys have Chinese Elm there (Ulmus parvifolia). That tree is about as good of a bow wood as you could possibly hope for and I guess it is an invasive non-native species in your country. Although it doesn't tend to not grow straight, it is hands down the best elm species and is as damn near an indestructible bow wood as you'll ever find. There is often some difficulty identifying it within its native range and other areas it has been transplanted, but it should be easy enough to ID in South Africa. It twists and checks a lot during curing, so keep that in mind and accommodate for it accordingly.
