After dropping in to the museum at lunchtime and lying down in the damp grass underneath the Sabre (No, it's not a usual occurance.) I discovered why the nose door rivets weren't showing up on my photos - there aren't any! It looks like the skin has perimeter rivets, but none inside that. It must be bonded or something. Taking them out actually improved the shape considerably. Nosewheel is now complete. (Yeah, right!)