OK so i've made my way up through the front dome cavity...
Right behind is padding/sound proofing material that makes access rearwards pretty difficult, so no easy direct line back...
There are plastic spacers running down both sides of the car but running anything down those won't help much (and there is already a wire bundle going down the drivers side) ...
Looks like a pull down of the actual headliner is in order if you're going to push on with this... i note the pop rivet in the centre and to the sides that i guess is to ease it but until I find out how actually hard it is to remove and place the whole headliner back on, i think i'm going to shelve this rear light for now !

Let us know if you proceed

(or if i decide to tackle it, i'll make sure to post..)
best of luck !
Blah... i found a guide on a mazda3 on how they remove their headliners... we're talking A/B/C pillar trims all off and then some so i'm going to pass on this and revisit if i'm seriously bored
