BA do not have buddy passes in the same form you do in the US. You have to register a companion or family to travel for a set period. BA nonrev now treats its staff badly compared to 10=15 years ago. If you have an econ ticket then that is where you sit .. even if there are premium seats empty as they will upgrade commercial econ pax to put you in their econ seat. You can elect to pay for a business upgrade ahead of the flight but if you do not get the upgrade you still pay the upgraded fare.