How do you replace the spring under the driver seat in a Skoda?

To get the seat out, first remove the plastic covers on top of the guide rail by popping out the small plastic bung to reveal a Phillips head screw, take this out and remove the plastic trim. Next undo the 2-8mm nuts with a 13mm socket push the seat back & tilt up slightly, push back all the way until the wheels come out of the guide rail, The seat is still connected by a tube with a wire running through it, unplug the cable and disconnect the tube. The seat can now be removed. unfortunately I am still working out where exactly the spring goes, if anyone knows please let me know DS