I've never done it but here is what the service manual says:
1. Open bonnet
2. Remove 8 screws securing wheel arch liners to bumper, release liners from wheelarch for access.
3. Remove 2 screws securing bumper valance to underbelly panel brackets.
4. Remove 3 scrivets securing bumper to armature.
5. Remove 2 bolts securing rear edge of front bumper to inner front wing.
6. Remove 4 screws securing bumper to bonnet locking platform
7. Applies to NAS models - Release side repeater, disconnect multiplug and remove repeater.
8. With assistance carefully lift and pull forward each side of bumper to release bumper side mounts and clips.
CAUTION: Always protect paintwork when removing or refitting any body trims or bumpers.
Note: I think these last two apply if you are discarding/replacing the bumper.
9. Remove front number plate
10. Remove badge from grille and discard clips
Hope this helps...
Brian