It’s when you go on holiday that you’re hit by the cost of weak sterling. I’m old enough to remember when my father came home with Deutschemarks for a family trip on the continent — and got 11 to the pound.In euros, that would be 5.5. This week’s actual rate is about 1.18. This isn’t simply a story of the UK’s relative economic decline because many things affect exchange rates, not least the fact that the pound was overvalued in the mid-1960s when it started plummeting.But..