Dozens of these insects flew in over a period of hours before sunset, throughout our campsite, onto us, on trees and into the grass of the swamp. Next morning there were none, but later that day they appeared again. If the ID is correct, Micalong Swamp at ~1000m is close to their max altitude. Also some of these were longer than I've seen described, at least one around 11cm +/- 1cm by my finger measurement.
Now that I look at the photos, these are completely different from photos of Purple-winged mantid Tenodera australasiae, I was mislead by the purple wings. These have plain very long forlegs and very different head shape, amongst other things. I can't find another match so looking forward to expert ID. I've added more photos in case it helps.
EDIT: I think Didymuria violescens.