Where will this all end? Aircraft operators have effectively been banned from flying in UK airspace by a combination of NATS, the Met Office (BBQ summer fiasco last year) and presumably the DfT.
It's very easy to play the safety card, but will NATS be stopping operators getting airborne that are flying into other parts of the world that are subject to volcanic activity? You can't fly to Barbados because you'll be flying close to Montserrat, Sicily is banned as well. No flights from the UK to Indonesia, just in case. After all, you can never be too safe. If this continues, they will be closing airports because the crosswind is forecast to get breezy or a CB is nearby.
Somebody, somewhere, hit the big red panic button. We went from a minor news story in northern Scotland to complete lock-down of London within a couple of hours. The problem they have now, is how to get things back to normal without losing face. And public confidence.