This is how I removed the plastic cover (the photos may not be in order):
1. Remove the two torx screws from the front of the cover.
2. Working from the back of the seat, slide a suitable trim remover upwards and under the plastic cover I used the flat handle of a wooden spatula). Slide the trim remover to one end of the cover and lever it up towards the side until it clicks loose.
3. Repeat step 2 on the other end of theplastic cover.
4. The cover is now loose and the seatbelt can be slipped away through the slit on its front.
Replacement is as follows:
5. There are two loosely held plastic pieces inside the cover. Make sure these are aligned straight before the cover is placed back on the head of the seat belt.
6. Place the plastic cover loosely over the head of the seat belt.
7. Feed the seat belt through the slit in the front of the cover.
8. Use a couple of sharp blows with the edge of your fist until both ends of the cover clips back into place. A piece of metal on each side of the seat belt guide hooks onto the inner side of the cover to fix it in place.
9.Re-attach the two torx screws to the plastic cover.