You were actually lucky in this image. The a curve controls the green/magenta and essentially the correction take the green and magenta out without touching blue/yellows. If a cardinal was somewhere in the image in a red suit, then this correction would have been more complex.No problems, Will. I'm usually stabbing the dark when it comes to intricacies of colour management so your example is a good one to learn from. It's always been hard to get colours right inside this Cathedral because of the combination of natural and artificial light. The GH1 has great white balance outdoors in daylight but can get tripped up indoors.
WB can really not compensate for mixed lighting situation. It can only try to find a point where two perpendicular axis, blue/yellow and green/magenta, is the most balanced.