Crow bar it open, then contact your insurance company since it has been broken into, and needs to be repaired.
Only kidding, of course. This would be illegal and irresponsible, and inevitably force up all our premiums, etc. etc!
It's a pain in the neck, but I think if you can put down the back seats, you should be able to crawl in and remove the plastic pannelling, allowing you to see what's going on with the lock mechanism and open it with a screwing driver type of thing.
Best of luck.