Thanks Steve. Skandix is never a good indicator.
I actually figured it out in the meantime, bit the bullet and twisted more than I was happy with, they do indeed twist 45° as mentioned by Cookeh, clockwise, and then you can pull them down and release the headliner enough to pull wires and/or fit an antenna. Here's a photo of the other side of the clip, in case anyone else needs it in future:
https://photos.app.goo.gl/mnwRywPp7tew8pev6
Now I need to figure out how to get my fish tape down the side to the sunroof, it looks like there's an extra large supporting rib there. Time to dig out the boroscope!