We are expected to do whatever it takes to get back for work in time and yes that does include buying very expensive last minute commercial tickets. BA has interline agreements with a variety of other airlines which allows us to buy staff standby tickets on their flights so that is an option but that obviously depends on their seat availability and they will always onload their own staff first before staff from other airlines. So BA won't do anything as such to get you home if on personal travel (other than releasing spare crew jumpseats, subject to the captain's discretion). If there are exceptional circumstances which could not have reasonably been foreseen by the staff member, then this may be taken into account if they cannot get back in time, but in general not being able to get a seat when travelling standby is not a valid excuse for being absent from work.