I've the same prob. There's a thread called "Rear seat catch" (sorry I don't know
how to link to other threads), but even with the descriptions from that thread I've still spent some of Sat morning sitting in the boot with a screwdriver and coathanger to try and release the set-back. It's worse for me as one of the rear-headrest was not in place when the catch broke - so i now can't put the headrest back in place (cos of the slope-y roof-line).
If you get the seat down - pls let me know how you worked your magic.