I do it fairly regularly and whichever option you go for, it's gonna hurt so aircraft choice is probably the most important. Especially in Y so I would go for either the BA11 and then onto the BA15 (which in summer down here arrives at 0600 not 0500) or the QFA380 (QF2) all the way. One of my best flights ever was on the QF2 LHR - SIN so definitely not a bad shout.