Not sure if this is correct, but according to the CEO of Germany's second biggest airline (Air Berlin), ALL predictions of ash dispersal and therefore airspace closures rely on one (yes - one) computer model run by none other than, you guessed it - the Met Office !
How anyone can trust ANY prediction from these muppets is beyond me. How you can base decisions such as closing most of Europe down on them beggars belief.
Again, not 100% sure of the veracity of the statement.