[Cookeh]

Simplest thing to do, to prevent this in the future, would he to add a cable from the power eyelet on the bonnet catch. Make it long enough so that it can reach an accessible point on the bottom of the car (fog light wiring brackets for example). Should your bonnet cable ever break, or your battery die as in this case, you'll be able to open the bonnet by simply pulling the cable.

I believe someone already posted the link to the more detailed thread. It's something I keep meaning to so but always forgetting about - if I do eventually have a crack at it I'll add some additional pictures to the original thread.