Hi Dave and anyone else interested (in Australia),
Beconase is available without prescription in NSW and QLD (they're 'Pharmacist Only' now). I don't know about anywhere else in Aus though.
Another thing, doesn't nasal spray called Otrivine (sp?) help clear your nose? This is I believe is also Pharmacist Only in Australia. I haven't used it in flight, so I am not sure if it helps with the situation being discussed here, though.