I have a set of S3 front seats in a S1 XJ... they are in perfect condition except for the rear vertical panels that will not stay in a fixed upward position.

The panels slide downward exposing the upper downward facing edges of the
piping on the sides. There must be a clip(s) of some kind that hold these
panels firmly in place?

A picture, part number or any information would be appreciated.

 

can't visualize what you're saying. Post some pictures?

 

Note the piping is loose... the panel below the horizontal junction moves up and down (both seats in the rear).. something is supposed to keep those
rear panels in place = upward.

Hope the photo helps in visualizing the problem? That upper horizontal edge/seam/junction can be increased by just pressing downward on the
vertical panel since there are no "clips" holding it/them in place. I do not have a S3 parts book and nothing is shown similar in S1/SII..

 

yes I see now, but there is nothing in the Service Manual about upholstery.

looks to me like a stress separation, coming undone at the seam. The only way to properly repair is to remove the cover, turn it inside out, and re-sew the area properly, which any automotive upholsterer can do.

 

If you can take the panels out, check if there's any (probably keyhole shaped) holes for clips.