I just searched the BA website for reserved seating and the following page came up:
https://www.britishairways.com/en-gb...sandconditions
It clearly states the following:
When you cannot claim a refund
- If you cancel your flight
It goes on to state in the detailed terms and conditions:
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.
You can pay for your seat reservation using Avios which is refundable if the flight itself is refundable.
- When Avios have been used as full or part payment, the Avios will be refundable only where the booking is refundable, please refer to the refund section of the Commercial seating policy for more information.
This seems inconsistent that if paying by Avios it is refundable but if paid in cash it is not.
I am not sure whether the above is specifically referred to when you pay as part of the booking process (you say not) but it seems that BA is right.
I am a Silver member so can reserve for free but would never pay to reserve any seat as I think that is a waste of money. I am not bothered whether I sit next to my travelling companion but in most instances when you are on the same PNR you get seated together anyway.
I do not agree with this policy and think you should be refunded especially as the Avios were and BA can resell the seats to another passenger. I wonder what legal redress you have as it seems a rather one-sided clause designed to favour BA.