I’ve discovered there are two species of yellow flowering Wood-Sorrel (Oxalis) which look very similar, and are often confused. One is native to Australia, the other is an exotic (weed) originally from South Africa.
Looking at the flowers of both species, I believe this could be the Australian native plant Grassland Wood-sorrel (Oxalis perennans). Can anyone confirm this? For reference purposes, the exotic species is Yellow Wood-sorrel (Oxalis corniculata).