Hello again, Mike,
That's encouraging that I wont possible ruin/break the plastic.
I've just looked on the Internet and found this:
If not, you can pull the door trim off, start at a corner at the bottom, run along the bottom and up the sides. The torx screws in it screw into plastic plugs which are clipped into the door, so at worst you might break those but they are one a few pennies each from your local dealer.
This was an old thread. It looks like I could actually pull off the plastic panel, without removing the fabric.
I might try this first. I should be able to undo the bottom two torx, with a right angled drive.
I might have to make up a thin steel strap with a 'hook' on the end to push between the rubber weather seal and the door. I'm not sure how that author managed to pry the panel off with his fingers. There's nothing to grip on.
The author of the above few lines makes it sound easy.