Good few hours work.
If the fob or emergency cable aren't working there is only one way to gain entry.
You have to take both rear wheels off and remove the rear wheel arch liners. This will give you access to the engine cover hinges above.
You need a couple of people because when you undo the last bolts in the hinges, the back edge of the boot lid will pop up from the pressure being exerted from the boot lid dampers in their closed position.
Once you undone the hinges, you'll need a long pokey stick to reach into the boot to hit the latch on the boot lid to release it. Again, another pair of hands holding the lid so it doesnt fall and scratch any of the body work as you poke the latch or lift it off. The glass ones are much heavier than you would think they are.
There are packing shims under each hinge, take note of how many went in each side. Also, the paint will have witness marks as to where they sat originally, use these marks for boot alignment when you come to do it back up
Ideally this all need to be done on axle stands as you'll be waist deep in the arches reaching up inside for the hinge bolts. You don't want it slipping off jacks.