Sorry to read of your poor experience.
I would edit your above post as appropriate and then paste it into the complaint form on ba.com to Customer Relations, request some compensation and then move on quickly.
The advice from those above is sound.
Hopefully you will receive an apology and some Avios, in addition to the refund of the seat fees. Five people were inconvenienced and not one, so make this clear.
You may receive nothing, which is why I would not spend too long on the complaint or dwell on the unfortunate situation.
Perhaps try AA for your next westbound flight?