Ive taken some shots while attempting to fix my lumbar support in my mk1 octavia vrs, thought that these may be useful to other members with duff lumbar supports...

to remove the seat, undo the two 13mm nuts at the front underside of the seat, you may need to move the carpet about a bit, and slide the seat all the way back to get to them. At the rear of the two runners there are small black caps covering a torx screw on each side. Undo the screws and pull the runner covers free, allowing the whole seat assembly to slide out into the back of the car. The seat can now be removed, remembering to undo any wiring connectors by squeezing the plug where it meets the socket, and pulling the plug free.

Pull the seat out of the car, without tearing the leather on the runner while manipulating it out...

Once the seat is out turn it upside down, I also found it easier to work with if the seat is wound fully forward.

At the pivot point of the back rest you will find a long black plastic strip, almost like a zip, which holds the front trim tight to the back trim. Its fiddly to separate the two plastic strips from eachother, I wedged a small flat screwdriver in the one end and ran it across the strip separating as it went along. You will end up with this...

then the two strips can be pulled apart and some access is now available to the seat innards...

now there is a stiff wire held in place by a couple of strong springs. You can get to them like this...

and here is one spring close up

you can use a pair of pliers to pull the spring away from the wire hook to get more room to work

and here is the offending part, a plastic rod connected between the plastic plate in the lumbar area, and the pull cable. totally snapped...

i used a spare metal P-Clip and bent it around a bit so it would fit the end of the rod and drilled through to screw the clip in place...

and although a bit crude, a spare bolt passed through the P-Clip makes a hook on the end. Remove the hook part thats left over from the broken rod, slide the cable retainer back into the large end of the rod, and pull hard on the cable and manipulate the back plate in the seat so the repaired rod hooks back under the plate.

Hope this helps, I havent refitted all back together yet but i guess its just a case of reversing the removal process

Pull the seat out of the car, without tearing the leather on the runner while manipulating it out...

Oh dear. :(

Thanks for posting this - could be helpful in the future

So that is what it looks like in there. At least i only had the cable snap so easy bodge.