My battery died the other day as well..
All lining around that area i took out.
Played around hoping i didn't have to take the brace that goes across the battery part.
Unscrewed that, took it off.. undid the battery, moved it around a bit and just slid it out.
The rear strut brace thing is the main thing that is in the way
If i didn't remove it, there wasn't enough room up because of the speaker. So couldn't get it straight enough to slide out.
Good luck.
btw drdoof, yes its in the boot, under the rear left speaker.