Unable to fold Corsa 2001 Rear seat?

I have a 2001 Vauxhall Corsa, with split folding rear seats. I've used this many times for larger items. Recently I went to fold them, (there's a latch built into the top of the rear seat that releases the mechansim holding the seat in place), the smaller split is fine but the larger side the latch seems to be detached from the mechanism as it just moves without releasing the seat. Anyone have any clues how I can get at the mechanism so I can drop the seat back?