Well not quite solved but I know whats causing it.
For ages i've had one of the worst annoying rattly squeaks from the boot of the car, new rubbers didnt help, silicon grease around the roof spoiler and boot seals didnt do much, fettling with the spare wheel and boot lining did nothing either but the other day I punched the roof lining in frustration and it stopped.
Gently pressing the lining in the middle also works LOL. It must be rubbing against the bodywork near the boot somewhere. So if like me dry sounding irritating squeaks from the boot area do your head in try the headlining as I would never have suspected it otherwise.