To remove the rear seats do the following
1) Remove the rear bench seat by simply pulling it up at each end. It is held in place by strong plastic clips. Just get one hand on the front edge and one at the side and give it a yank. Don't be scared, it's the only way.
2) Remove the two Torx bolts holding the rear seat backs in place. These are at the bottom, middle of the seat back in between the seat belt slots.
3) Release the two spring loaded clips from, inside the boot, underneath the rear parcel shelf. They are a bit of a pain in the ass, get a large flat bladed screw driver and push them towards the side of the car.
This video shows the way. http://www.google.co.uk/url?sa=t&rct...UCMrmaq_duQyA.
Once fully engaged they will stay open, only closing again when you replace the seat back by giving it a good hard push back into place. They open against a spring into a little catch, when you push the seat back in hard they snap shut again.
If you are only running the harness through you should be able to do this just by doing all of the above and leaning the rear seat back forward a couple of inches. Be careful as the seat back once released rests on two metal hooks at the bottom two front corners, inside the car. If they pop out and youre not ready to catch the seat back it will fall and likely scratch up your rear door sills so be careful.
Good luck with the install, sorry for not replying to the PM, I've not really been on the forum for a couple of months!