Unfortunately it is a fast spreading and very destructive fungal disease. I would get it out of the area ASAP. It can spread through droplets so it makes watering a real challenge. Botrytis thrives in humidity, hence the reason it is a grower's nightmare. You can treat it w/poisons but I found few very effective. If you decide to 'wait and see' remove any other plant material w/in shouting distance. It's just not worth the risk to your other plants. Hope this helps.
Thanks Susan, Is there any chance I can save this plant? It appears Botrytis is a killer, 2 leaves have already dropped off. Should we just destroy the plant, it's affecting quite a number of the leaves and if I remove them I think the plant will look odd or even ugly. What's your recommendation?