For such a straightforward trip, it's probably easier to use matrix.itasoftware.com. This will also give an exact breakdown of all the taxes, fees and surcharges.
In summary (assuming the return fare is around 4.5K)
* fare basis is AAP9UK
* min stay Sat night
* max stay 42 days
* BA and QF flights only
* one stop permitted in SE Asia
* GBP200 cancellation charge before travel commences
* no refund once travel has commenced
* GBP200 change fee (plus fare difference if no A inventory)
* valid for travel commencing between 21/7 and 02/9
* tickets must be issued on/after 06/6 and on/before 14/6
hth