BA SOP is for no seat power to be activated below 10,000ft. If the aircraft can do this automatically, crew need take no further action. On older aircraft, it needs to be actively switched on once the correct altitude is reached. A quick reminder is all it takes if they haven’t done so.

Most - but not all - of the ceos now have working power sockets. I find most crew announce at the start of the flight if it’s inop on that specific aircraft to save people trying multiple wires and sockets. Assumes the pax listen, of course.