Rather interesting SIGMET covering most of Europe at the moment: SIGMET VA - volcanic ash! If you look at the content of the SIGMET, it contains EXERCISE for the VA bit. Ties up with the report on this site about "exercise Volcanic Ash products":
https://www.metoffice.gov.uk/aviation/vaac/vaacuk.html
Interesting that they've actually picked a possible volcano to erupt and modelled the winds?