Monumental Farce!
The disparity between the two published ash cloud charts from the UK Met Office & Eurocontrol combined with NATS's and Eurocontrol's respective differing interpretations of flying in what essentially amounts to the same contaminated air warrants causing this entire event to descend into a monumental farce.
If NATS's so called "zero tolerance" interpretation of the ICAO regulations regarding flying in volcanic ash is correct then I trust they are taking down the registration details of all aircraft currently being flown within the contmainated area over mainland Europe prior to issuing future bans on them ever entering UK Airspace.
After all we wouldn't want these entirely unsafe aircraft to enter UK airspace risking multiple engine failures and randomly descending onto the heads of the very unsuspecting citizens which they are currently going to such extreme lengths to protect!