I find that silly since taxes and charges are normally set externally and Mennens essentially allows BA not to be out of pocket for charges and taxes that it cannot control. Here YQ is part of the fare, it is leveraged by BA just as much as the fare; and BA has gotten away with it because YQ is seen as the same in both First and Business cabins. Furher compounded by being in a BAH booking so the individual taxes are not shown. There is nothing to stop BA making every fare £1 and everything else Carrier Surcharge.

I think further claims of this sort had better go via MCOL. That is still open to the OP, but I wouldn't be surprised if they feel they that have had enough of this.