corporate-wage-slave

Just to give a bit of background here, if a flight is held overnight, and therefore is expected to run just very late, then the reservations are kept on the flight, boarding passes would usually still be valid (depending on the airport's own gate system) and it obviously makes check-in / seating very straightforward. On longhaul with perhaps one flight a day this is realistically the best way of working; however AGP is almost at the other end of the spectrum since when operating normally it's actually one of the best connected airports in mainland Europe in terms of routes to the UK. But the downside to that is anyone who wants to go on another service has to be offloaded from the flight, and it's not necessarily evident to the Contact Centre staff that something has gone wrong with the flight, at least initially. Being offloaded would normally be only open to those on flexible tickets in normal circumstances since most tickets sold wouldn't allow for a flight switch without extra charges. The app / BA.com still has the flight working as normal so no option there either.

That said after 2 hours delay informally, and 5 hours formally, people are free to seek alternative arrangements and so Contact Centres tend to be helpful then. The 5 hour aspect is both in the Conditions of Carriage and EC261, and it's worth bearing in mind since in addition to being rebooked, the passenger can get a refund, and thus look at other airlines if the airport isn't rebooking people.