Thanks for those Janet. I checked them but the neither the Merremias nor the Calystegias have the same winged stems and petioles. And the leaves don't match, particularly with the Calystegias.
I did some further checking of our local Convolvulaceae (of which there are about 80 species) and narrowed it down to Operculina, of which there are only 4 species here:
aequisepala
brownii
sp. Cotton Island
turpethum
Couldn't find any images of the undescribed species (sp. Cotton Island) but the best match of the other 3 was O. aequisepala. It appears all the Operculinas have the winged stems and petioles. This one is native across the north of Australia, but also occurs overseas, probably South East Asia (the reference didn't say).
It's rather strange, in all the years I've been bushwalking here and the areas covered, I've never seen this plant before. It had to come to me.
