Are you able to advise me on caring for a newly planted (presently only 80cm high & virtually bare) clematis napaulensis please? I live in Melbourne Australia which has warm-hot-dry Summers (now) and cool & fairly dry Winters (rare fronts but no snow).

I have been growing this species in southern UK for seven years with no special treatement. There is a picture of its flowers somewhere among my photos.
Like all clematis, it likes a cool, moist root run with its head growing up into the sun. I would say just make the sure the roots don't dry out, especially while it is getting established, and it should be OK.
One thing to note - it goes into a summer dormancy (July/August over here) so if it looks like it's on the way out, don't panic!
Good luck