Originally Posted by
DeathSlam
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?
You cant add extra baggage this way, you can only ticket as a hand baggage only fare or a baggage fare. Its the same as the choice you get if you book on ba.com.