They should twist in, but its not a 90' turn, more like 45' if I'm recalling correctly. To slide headliner outyou need to remove all the trim surrounding the headliner. That is the A, B, C, and D pillar trims, the trims that run between them along the top of the doors, and all the grab handles, sun shades, rearview mirror and map reading lights.
With all that out of the way, you should find that the front of the headliner is already free and drooping down. You can then remove the clips that you linked to - alternatively, you can try sliding it forwards until they drop off those clips.
Half decent forum post on it
here. It is a US sunroof car so some slight differences but you should be able to get the gist from it.
I did have a whole bunch of pictures on the process but when TinyPic went down I lost them.
It really is a 30 mins