You'll find most if not all, airlines will tend to wait for the NOTAM shutting airfields/airspace to be issued before pulling the plug on any operation. Unfortunately NATS don't play to the same lead-time as most airlines and trying to "do the decent thing" by giving passengers early notice before a NOTAM is issued has back-fired recently. I refer to the last closing of Scotland a few weeks ago, airlines cancelled late the day before only to find out when the NOTAM was issued it was only the west coast ie, GLA/PIK that was affected.