The carrier surcharges are higher for ex-US than ex-UK bookings. This has been discussed a number of times.
And what exactly is the justification for that?

It is really quite off-putting dealing with a business that seems to have a deeply ingrained culture of "We can get away with screwing yet a bit more out of you -- so we will." Every time I think I've plumbed the depths of BA's shark-like practices, I stumble on something else. There seems to be no end to it.