I had a research fellowship on the transport of volcanic ash from Icelandic volcanoes to Europe. I wrote a number of blog post explainers.
These are best for context.
+ We'd expect an ash cloud to reach the UK about once every 20 years: https://all-geo.org/volcan01010/2011/02/ash-cloud-closes-airports-chances/
+ A history of ash clouds and aviation: https://all-geo.org/volcan01010/2014/02/a-history-of-ash-clouds-and-aviation/
+ An Icelandic eruption 100x more powerful than E2010: https://all-geo.org/volcan01010/2012/04/an-icelandic-eruption-100-times-more-powerful-than-eyjafjallajokull/