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I have recently agreed with my student partner that she will move into my flat during the Edinburgh Festival so that she can sublet her room and pay for her half of our holiday together. She maintains that she should pay me for staying in the flat, whereas I argue that this would defeat the purpose of the exercise. How can we effectively resolve this dispute and look forward to our holiday? Should I simply charge her for any increase in my bills, or are there other considerations? Ben, Edinburgh

Going overdrawn can be an expensive business. In the UK, unauthorised overdrafts averaged £680m on any given day in 2006 – just over £10 per bank account. According to the Office of Fair Trading, the charges levied by banks on those overdrafts were £1.5bn, a tasty return of more than 220 per cent. Banks also make money by paying risible interest on positive balances – an incentive to keep your current account lean and, Doh!, to overdraw accidentally – and by other obscure charges. The Office of Fair Trading doesn’t like it and nor do many customers – although they rarely express their displeasure by switching bank accounts. There are two common responses. People either grumble about money-grabbing banks or point out, smugly, that if only others would manage their affairs responsibly, they wouldn’t incur any of these charges. There’s a certain amount of truth in both responses...