Removing E39 front bumper.

I can usually sus things out for myself, but this has me stumped. My problem is removing the black grilles alongside the fog lights, to get at the upward facing bolts holding the bumper. According to an article in a roadfly.org forum, once the pin fasteners have been removed from the top of the grilles, the grilles should just pull out, allowing access to the bolts. After removing the fasteners the grilles are still firmly hooked behind the bumper, top and bottom. They're loose, but even after tugging almost to the point of breaking them, both the upper and lower edges are still trapped. Either I'm pulling them in the wrong place, or there's a knack to it which I haven't found yet. Both headlight units are out, and I have removed the bolts from inside the wheel arches. The main bolts concealed by the grilles appear to be the only thing stopping the bumpers removal, so any help would be appreciated. I'd like to get the job finished tomorrow. TIA. Mike.