On arrival from Australia into LHR, you will have access to the BA Arrivals lounge, your wife however will not so if you wish to use it, you will have to leave her outside

The rules of departure lounge access is that you plus a guest are entitled to 1st and business lounge access prior to departure of a flight when travelling on a OW marketed and operated carrier

As a QF Platinum member you are entitled with NO guest to use the BA Arrivals lounge when arriving on BA or QF

As a QF Platinum member you are entitled to a treatment in the Molton Brown Spa prior to departure on a QF long haul flight


Dave