Does anyone know how to remove a rear seat from a vauxhall crew van?

The mechanism has failed and it is locked in place. You push the button on top of the seat down and it should release the seat. However, it seems something has broken and when you press the button down, it just drops, failing to push down the peg to release it.

You cannot get into the small space at the back of the seat to manually push it down and I cant find any screws or anything to undo on the back of the seat to be able to get into the seat and mechanism itself?

Any help appreciated, as I cant see any way to resolve this.

Thanks,

Pricey, May 2009