get in the back, take the pannel off the inside of the boot (annoying plastic screws which you WILL loose) and then just pull the control rod. that will get you in and then check the lock is ok, or the rod hasn't fallen off or something
there should be a green plastic clip on the back of the barrel, connected to that is a grey metal rod that goes down to the latch in the middle, this needs pulling to open the lock, if the rod is not there then that is your problem