I get the feeling it can be a case of keep asking different agents until you get the answer you want with this.

On Wednesday I flew LHR - DUB and wanted to travel earlier in the day. Initially I rang the concierge line and was told I’d have to pay the fare difference (that’s not true). So, I hung up and asked at the check-in desk. There I was told to come back c. 40 mins later (just before the next flight was closing check-in) to see if they could accommodate me. I then called back the concierge line, got a different agent, who rebooked me immediately without problems, without charges. So, I got to travel three hours earlier than scheduled.

Another time I travelled earlier from DUB, the check-in agent who amended my booking told me that at a push sometimes they will change to the previous day. I guess this is a loose interpretation of the 24 hour rule. Too dodgy to rely on though, in reality.

On another note, I’ve had similar experiences when booking through ticketed connection flights via DUB on European flights. If you get a concierge phone line agent who agrees the 120 mins connection time is excessively cautious, they can agree to make a reservation where another agent refuses.