I have a BA ticket CAI-LHR into T5 and them LHR-SYD on QF from T3. Traveling with only cabin baggage. Will BA be able to check me in through to Sydney? I've linked the PNRs, but QF just advised on the phone that: "Another carrier cannot check in a Qantas flight" which just doesn't sound right. I've done the same itinerary above, however booked on the same ticket.
QF advised that I literally had to wait around until QF check in opens at LHR, 8 hours after the first flight. Why wouldn't I check in online and just head to the T3 GF Lounge?