Last year I did a big study of Irish companies, looking to see which ones were most indebted. To my disappointment, the great majority of them were not heavily indebted.  As a group, the rise in interest rates didn’t hurt them much.  The exceptions were mainly the Irish companies that had gone to the USA. Those companies had more gung-go American-style attitudes to debt. Ardagh was one of them. Ardagh is Paul Coulson’s glass and metal packaging giant. It has 65 factories. They are mainly in Europe and North America, with a few more in Brazil, South Africa, Ethiopia, Nigeria, and…