Volcanoes in Iceland and other safety issues in the UK

Britain is paralized! says The Sun this morning. That doesn't mean that I'm reading The Sun but that it's the second day Britain's facing major air traffic disruption, because of a volcano in Iceland.

I was quite surprised as I heard the news that all domestic and international flights in the UK were cancelled because of a volcanic eruption in Iceland. How come? I mean, yes, I assume that volcanic eruptions might me quite, well... massive. However I've never seen one before. So I was watching the sky looking for ashes. But I couldn't find any. So what's the problem? Why can all the airplanes not fly?

However there's another quite interesting aspect in this whole issue. An aspect that shows us again that borders aren't really existing, even if they are built of thousands of miles of water. So even if a country is geopgraphically and geologically separated from other countries it may have major influences on them. It may be closer than thought. Not only in terms of natural catastrophies. Worth keeping in mind!