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I have done this a few times mate. You have to lift up the back seats, and unscrew the bolt which screws your rear seat belts to the car (underneath rear seat). You then need to open the rear window and remove the seal. You may also need to remove part of the seal on the front door. There are door panel clips on the sides of the rear panel which should release by pulling the rear panel upwards. Then there is an awkward piece of plastic shown in your first picture(near where the seat click in), which needs to be liftedd with a screwdriver. As you lift that, pull the panel towards the front of the car and it should come away. It is a pain tho lol. Once you done it once its easy.
Hope that helps mate. Let me know how it goes