I stripped the whole thing, laid it on a big table, sprayed glue everywhere, strretched the old vinyl back into place, stapled it as per the original, strenthened that with a gazillion bulldog clips while it dried, stretched it into place with bags of sand to weigh it down into corners....
The result was shite. :-( The vinyl just will not stretch into the corners.
Tried using self-adhesive sound absorbing foam, concerned it would not stick. The adhesive stuck to the roof all right, just that the foam did not stick to the adhesive.... I've now got two bits of foam on the floor and a layer of adhesive on the roof....
Currently driving about with no headlining. V. Noisy and lots of condensation. :-)
Ideas welcome.... Next step may be to try re-covering the old headlining inner with some new fabric ?