Is there lots of play on the gear stick ?
If you lift the gear stick gater cover and move the stick from side to side does it move a long way in the socket ?
There is a part on Ebay you can buy to repair this socket;
http://www.ebay.co.uk/itm/Repair-tools-kit-Jack-ASTRA-VECTRA-ZAFIRA-COMBO-MERIVA-gear-box-model-F-23-/321350268216?
I ended up £170 down as I needed the car asap for work but if you have time to wait for delivery and an afternoon to fit then the feedback suggests these are great and work !
Paul
March 2014