Personally, I think BA's position is disgraceful, especially given the programming of their web site, which changes any number of things when you hit the "back" button, depending upon exactly what you're doing. Is the information presented to you, clearly, on subsequent screens? No doubt. And so what? It can be a confusing and sometimes (needlessly) complicated process. What's the harm in giving someone a 24-hour grace period in a situation like this. I know of at least 4 or 5 other major airlines who do so and it appears that there are many more. Sure, there will be the odd person who takes advantage of the airline, but by far the majority of changes will be from people who made an honest mistake (and will be grateful for the courtesy). I try to be very careful when booking and have messed up twice myself. Fortunately, it was with airlines with a more customer-friendly policy than BA.