I can only give you vague help but others who have had to do it will be more informative.
You have to go from below with some kind of rod or coat hanger type wire and poke around until you can grab the little bit of cable showing and yank on it to make it pop open.
Underneath the cross-member that holds the latch is a flitch plate that gets in the way.
I think once people have had this problem they discard that plate to make it easier next time!
Although I have not had your problem I did remove mine when I was rustproofing the car and I can see how it obstructs things.
Good luck...help will be along soon.
Its a well known Achllies heel on these cars as you probably know same as the useless 'superlock' feature which permanently jams the passenger door when it goes wrong.
Try to access from underneath the front of the car whilst on axle stands or ramps. if you are lucky someone will have had the good sense to remove the nuisance plate which covers the underside of the bonnet lock so you can just jiggle the latch and release it. If not then I think you may need to find a way of cutting or grinding to remove that plate.
Why on earth it was installed in the first place no one knows. - to protect a spare wheel which wont fit any other car or maybe to stop confused ravers wanting a fix of battery acid.
