We have data; government aircraft from several nations, including the UK have tested the air quality and stated that its is not good enough for aircraft to fly.
As far as it was reported they found gases that are produced by volcano, nothing was said about the abrasive hard particles.
One might expect that the gases in a cloud should be able to travel longer distances then hard particles as hard particles are subject of gravity.
It is 1179 miles from Reykjavik to London.