Hmmm.....
Just checked - it is D !

It was J (so many changes have been made to this and business class flight from the deep south to LHR was thrown in yesterday - all done through the travel agent and I have no idea what they have done or why). So it must have been re-booked entirely.

In any case - paying is not really the issue. Happy to do that for an upstairs window. Unfortunately it looks like a no go. Annoying.