James,
I don't know how much this will affect your plans but all the BA flights from SIN/BKK/SYD and MEL back to London are embargoed for standby travel from 26MAR04-09MAY04 ( weight restriction due cargo load ). Note the outbounds are not yet embargoed so if you have dates and think you may use BA then list ASAP in case they put on outbound embargo.
For reference at the moment flights to both SYD and MEL outbound early to Mid April and return early to Mid May are wide open.
Paul