OMG So BA lost your Emergency Exit Row and your coming here to complain. Well at least you got to your destination in one piece. If the Emergency Exit were so important to you you would have refused to take the flight in the first place.

But since you took the flight and accepted the new seats BA owes you nothing. You could have stated to the Gate Agent to see if Emergency Exit or extra legroom seats became available.

I can guess the next thing you will complain about is the food was bad. The washrooms were not cleaned properly. The Champagne they said was Champagne is Sparkling Wine.

You got home safe and sound so don't expect any compensation. You may never know when you need to write BA for something major like my Chirstmas Trip flights were cancelled without telling me and I'm forced to buy a new ticket. Well they go into the Complaint History and see you have complained about a small item like a seat assignment.

Remember your seat is actually on a request basis just like a special meal the airline can move you if they need to. You are not owed that seat and because you were switched from another flight the people currently seated in the Emergency Exit should not be displaced because of you.

How would you feel if you boarded your nice First Class seat only to be told by the Cabin Director that we need your seat and they put you in the last row of Economy Class because they know you love to complain about your seat location?
Sorry to burst your bubble