EWL, will be interesting to see whether you can purchase a ticket from British Airways in Australia, or whether you have to ring USA.
You are a little luckier than some at least you should be get yourself an affordable airfare, to get to either JFK or LHR.
I am wondering whether you can start the non Concorde flight in another US British Airways gateway city.
I am sure you will give us an update on how you get on.
Good luck.