I don't know the model of corsa you have, but here are some suggestions.
1. Look at the latch, is there a worn off sheath of plastic on it. Quick fix is to wind insulating tape around the keeper.
2. With the boot open, push in the clasp of the latch and see if it locks into place. This will tell you if the mechanism is damaged. Remember to push the button before trying to close the boot again.
3. Look at the keeper in the frame it might be slack or have moved.
Jmmy, June 2010