Posting here to shed light on the relevant T&Cs
https://www.britishairways.com/en-gb...es-and-refunds

Refunds
You will not receive a refund for paid seating if you cancel your flight, are involuntarily upgraded or do not meet the requirements to sit in the seat type you have selected.

On British Airways marketed and operated flights, if, in accordance with your ticket type, you choose to move to a different flight, you will be entitled to choose an equivalent seat on your new flight. However, if an equivalent seat is not available, the difference paid will be forfeited and will not be refunded.

On flights marketed by other carriers, if you choose to move to a different flight, you will not be entitled to choose an equivalent seat on the new flight and you will not be entitled to a refund.

You can apply for a refund up until 30 days after the last flight in your itinerary.

Please submit your refund application online using the Seating refund form. We cannot process refund applications at the airport or on board.

Unless otherwise stated, we will only make a refund to the credit card used to pay for the pre-assigned seating, or in the case of Avios payment, to the Executive Club Member’s Avios account.