Originally Posted by
Anonba
This is actually a common scenario as anyone taking connecting flights with another airline + BA can only pay for extra bags at the airport. So the airport should be used to this.
Not exactly the same, but I had a BA ticket on another carrier (an award ticket and not mixed with BA) and managed to get the baggage changed by getting it reticketed.
It's probably not economic to reticket a cash booking to add baggage compared to buying it at the airport (so doesn't help OP) but I wonder if it would be possible for a phone agent (or TA) to add extra baggage at the time of booking?