Everybody. Everybody has an accent - especially since it was before any sort of standardization, like RP of today, and we really can't tell what was the accent before modern recording devices.

Both free settlers from UK and the convicts were derived from various counties and countries - around 12% of convicts came from Ireland, for instance, and many Welsh convicts did not speak English.

A significant number of settlers were Londoners, and perhaps this was the basis for what's today an Australian accent, but the population varied wildly.