hi weg, i think you will probably have to get on your back underneath the front of your car looking up at the bonnet catch ( you will probably need to use a torch ). and using a long screw driver or something similar manipulate the catch to the open position your bonnet should then pop open. if you can see the catch looking through the front grill you might be able to poke the screw driver through and manipulate the catch to the open position that way.
good luck.