From a quick look arount the internet it appears that the Zafira has a hydraulic clutch rather than a cable - which sounds right.
From the description it doesn't sound as if the actual clutch has failed which leaves you with most probably Master cylinder, slave cylinder or pipework
Depending on type a pattern part (as opposed to a Vauxhall one) is going to be £75-120 plus more brake fluid plus say an hour's work to fix maybe £200-250
However clutches 'can' fail in more creative manners - I've had a Landrover slave wear a hole in the cluch fork causing a sudden failure like that and you have to get inside the clutch housing and replace it.
Can't tell for sure without looking but probably a master or slave failure