I actually find the straight-through London-Aus/NZ jetlag to be remarkably easy to deal with, even in Y.

I treat each flight as a night: sleep as much as possible on the first leg, get up, get off the plane, shower, get back on the plane, more sleep, then wake up at destination pretty refreshed.

The effect for me tends to be an early wakeup, early bed routine -- and as a natural night owl by inclination I find it quite pleasant to be on an alternative schedule for a few days.