Exciting stuff. TopGear also went up there but that was before the volcano started erupting beneath the glacier. They drove over the glacier, directly over Katla. Imagine if Katla started erupting with them on the glacier. The ground would literally melt beneath them in a 10km radius, and they would be about 800 meters above an exploding volcano.
BTW. although there are volcanoes, Geysirs, glaciers, rivers and other natural phenomena as well as vast uninhabited expanses that you don´t want to get lost in, such as the biggest desert in Europe (not a dry desert though) Iceland is a perfectly safe country to be in. An exciting and beautiful country.