I had the same problem hamilton, in that Keif's awesome post didn't work for my 750Li. Unfortunately, I don't think you will not be able to remove the the headlight without opening the hood. I removed my bumper and headlight to replace my cables after an INDY got it open for me. He charged one hour labor, but said that it took longer and would charge more in the future for 750's. He was not able to release my latches but he was able to take a long pair of pliers to reach the cable leading to the first latch. He yanked it real hard to release the first latch and in doing so it released the second latch in the system as well. I do think that it is worth a try to pull the cable iside the car after taking off the bonnet because of the reason your hood may be unable to open. It may just be lodged in the cords. Hope this helps, good luck.
2007 BMW 750Li w/ Comfort Access and Soft Close Doors
Luxury Seating Package w/massaging driver seat, ventilated front seats, a heated steering wheel and rear sunshades
Premium Sound Package w/ 13-speaker Logic 7 sound system with an in-dash CD changer
Staggered Chrome Rims/Michelin Pilots & BMW Centers