The other thing to consider is if it is Austrelaps, then the only one around this region is ramsayi and in both Austrelaps the diagnostic character to confirm id is the pale anterior edges to the upper labial (lip) scales, never present on Pseudechis. The pale edges give an appearance of white lips or teeth, not to be confused with the white line on the smaller, White-lipped Snake. That's why we prefer an image of the face, have a look at the picture of one to get your head around what I mean.
I mean given the location and the quality of the image I can definitely understand going with the redbelly... To me it just didn't give "redbelly" vibes and was kind if leaning to a slightly browner tone... But definitely willing to accept that the photos are inconclusive and redbelly is what makes most sense...hopefully I'll get lucky enough to find the same snake in the same kind of location again and that might confirm (or not) that it was definitely a redbelly. Thank you for your explanation! I always appreciate getting better insight into how I can provide better evidence or make more accurate judgements myself.
Not much to go on here but given the locality, I am inclined to agree with Patrick that it is most likely to be a Pseudechis. It would have been handy to have had a clear shot of the head and the dull colouring may be because this animal is about to shed its skin. On larger specimens the red flush is often not all that apparent.