How did you get to the two screws on the rear card that are behind the seat squab without taking it off?
The pax side was easy as you just dropped the split seat and the two screws to the rear are exposed and then it's an easy removal of the rear trim - obviously the base needs taking out. Drivers side more awkward as you need to push away the edge of the seat to get a screw driver in but it came out ok. Refitting was fiddly on that side and I haven't re-screwed the rear ones as I need to get it out again this weekend to do the hole repair. Not sure it's gaining you anything by not removing the back but it's possible
This is the 16v so perhaps the 20v's have a different split seat set-up so doing the above may not be possible?