There's not much point arguing, but I just have to make sure there's a dissenting opinion on here - it has been publicly admitted that no one has a clue about the actual ash densities within the cloud. Consequently, the density over AMS, CDG or FRA could be as high or higher than over the UK. At least if those ash cloud maps are correct.
If they are, and if KLM, LH, AB and loads of others can fly and land without problems, and BA decides to play "chicken" and gets declined by NATS, then I have to side with BA.

IMHO there are some hurt egos at NATS now who have to justify their overreaction and to show that they know it better than "the continent", and BA is suffering for it.

I'm really looking forward to the results of all the investigations into the realities of the cloud. Six months from now, it'll all probably look pretty laughable...