YES YES YES!!
Brilliant. I can even turn off and configure the overlay using this. I was about to bin this camera!
Whats happened here is that by default, CMS finds and selects the onvif stream and lets you view this. You need to manually change the port to "34567" to enable the configuration options. It's insane this isn't mentioned anywhere on the product page or docs for this camera. I might actually buy more now that I can set them up as I want.
Thanks all, especially pozzello for the images!
EDIT: and on another note, as this camera only supports onvif 2.0, you can't actually use onvif to set up a H.265 stream anyway.