BA first has two type of revenue ticket, denoted by fare bucket letters: F and A.

F tickets are fully flexible and refundable; A tickets are less flexible and cannot be refunded if cancelled. Obviously F is considerably more expensive than A.

In this case I think you are stuck with your existing tickets.

But c'est la vie, it could be that the current price for the route you hold is considerably higher than the price you paid.

That's just a facet of airline ticket pricing (and many other things in life where you won't be able to get a refund just because the price has dropped).