I am pleased to report that option 2 was successful. I sailed past a lovely C lounge dragon who asked me "You're OWE, what are you doing here?", and was probably helped by a subsequent flight having been cancelled, increasing the likelihood of them being able to use my original seat. On the occasions I've dealt with these agents, they've always been extraordinarily helpful and extraordinarily competent, and this was no exception — they're a credit to their employer.