I've used American English file with adult classes. Great book, loads of material: workbook exercises, communicative tasks, pronunciation activities, and supplementary material; and the teachers book is actually quite helpful. Someone told me there's actually a British English file that follows the same format, can't verify that though. There's so much material with the three books that I'm sure you'll find something you can use for a one-to-one lesson- only problem being you have buy the three books!