APD + BA change fee £25 + using phone £15 + any other fee that BA could think up while you we're on the phone. It isbpossiblebthey charged young change fee for each and every flight that was changed or altered.

I note the OP says that BA stated taxes which is not only misleading but thoroughly dishonest and exactly how BA describes their fee structure in my experience.

I was charged £160 for changing an F redemption less than 8 hours after it was booked to an open jaw which cannot be done on BA.com.

It is a fee ridden airline and the Ryan air of full service carriers. Know that, understand it and either live with it or fly on some other carrier.