******* thing has gone on me 3 times now... this is how i now fix it
pull down rear seats
remove parcel shelf
remove 3 screws holding the panel in, 1 is inside the grab handle on the inside of the boot plastics, the other 2 are under the removable covers for access to the rear fog lights
grab the plastics just above the rear washer motor and pull like F***
it will sound bad, but just get on with it, you shoudl now have a gap enough to get your arm into, just reach in and pull on the boot release rod.
if the above sounds too rough then you can do it slightly differently. but takes much longer
pull down rear seats
remove parcel shelf
remove 3 screws holding the panel in, 1 is inside the grab handle on the inside of the boot plastics, the other 2 are under the removable covers for access to the rear fog lights
disconnect the speakers in the rear
remove the holders that the speakers are in
grab the boot plastic again from above the rear washer motor and pull, this time it should be possible to nearly totally remove and you can see the boot latch to pull upwards.
hope this helps
Marc