Before we start arguing about the semantics of llanfairpg refusal to orbit on final, let's all agree that this was a highly unusual request at a highly inconvenient time. I'm sure all of us have had one of those one way or another
I've never been asked to orbit on final! - I've no idea what I would say, but I wouldn't do it.
I
have been asked, on final for the tarmac, "can you reposition for the grass (parallel runway)", to which polite request one can say "yes, sure" or "no thanks", no "unable" is necessary; but following Southend the controller isn't even allowed to ask that any more.