1985 jaguar sagging headliner behind sunroof.. it is definetly the headliner and the headboard you can push the whole thing up but it just sags again. Detailed instructions on how to replace would be great.

That  sounds like the headliner has turned loose and has a sagging bag just behind the sunroof opening.We have an online guide for installing a 98 Jaguar XJ8 at this link, this should help quite a bit. May not be exactly the same car, but they will be very close to the same.