What do the two "Buttons" do? And can the two "Side Panels in the Boot be Removed?
The 2 buttons are part of what is holding it in place. I think lots of trim needs taken out before you can get at the real fixings. The boot side liners, the rear pillars all need to come out first. Not sure how to deal with the airbag in the pillars. There are videos online for the saloon but I’ve yet to find one for the coupe. They’re quite different. The saloon is more of a cover where as mine has the whole rear brake light assembly and the Harmon Kardon speaker system all built in. I just need access to stick some soft Velcro strip along the window between the brake light housing and the window. But can’t get at it. If the speaker grille would pop off I could check the integrity of the speaker itself but it’s not coming off easy and I’m afraid of breaking clips. I thought there were You tube how too’s for everything these days. But not this apparently.What do the two "Buttons" do? And can the two "Side Panels in the Boot be Removed?
The "Airbag" Covers can be lifted using suitable "Plastics Tools" they reveal a "Clip" that keeps the "Airbag Cover " in place, care is needed to avoid the "Airbags" themselves!
You may then see if the "Parcel Shelf" tilts forward! 
I’ll have a go at leveraging that wee “airbag” plastic cover in the pillars. See what that reveals. On the saloon you can grip the seatbelt cover and pull forward to slide off the pillar trim however before that you have to remove the rear door trim (which I obviously don’t have). It would seem you have to dismantle half of the back of the cabin to get the shelf out! It will be an exercise in exploration and may ultimately be taken to the Dealership in bits.The "Airbag" Covers can be lifted using suitable "Plastics Tools" they reveal a "Clip" that keeps the "Airbag Cover " in place, care is needed to avoid the "Airbags" themselves!
PS: It helps folk that have replied to any of your Posts if you utilise the "Reply" on the right-hand side, it alerts them that you have commented!
Any speaker grilles I know of do just pop off. I have leveraged the centre grille somewhat but it isn’t coming easy. Scared of forcing it and breaking it. I appear to need the shelf out to solve the brake light against window issue anyway as access is basically impossible due to the angle between window and shelf and the depth of the shelf. Unless you have four arms the length of an orangutan.
