It might have escaped your notice (maybe because the Daily Mail forgot to tell you about it)
but planes have been grounded all over Europe and as far away as Ukraine and I believe that the decision to do this was taken by the relevent air traffic control bodies in each country (NATS in the UK) and has absolutely nothing to do with either government or over zealous health and safety officials.
It's OK for you moaning on about it from the safety of you armchair, but would you like to be one to make the decision to allow these planes to fly if there was even the slightest possibility that they may fly into this cloud and fall out of the sky.