You can avoid the monster tax by taking for instance a LHR PAR or LHR FRA flight on a seperate ticket and only pay the EU half price shorthaul tax and then pickup an AF/QF codeshare ex PAR to SIN or the QF 6 to SIN.
The LON Europe leg should idealy be on a seperate ticket and provides a chance for a stopover at an extra destination.
BA are pretty cheap internally one way, and for the airlines with high oneways, we haf vays off making zem cheap!
Many ways to skin a badger but what a stupid move
Just another way of gathering taxes that will most likely never see anything greenish - good thing in a way - just encourages the bastards.