Not sure if this is the place to ask, but here goes. I am planning a trip from the UK to Australia, and, for various reasons, was thinking of doing the following: namely, getting a C class return LHR-SIN on LH, and, separately, buying a Y class return SIN-MEL on SQ.

However, I'm a bit unsure about the rules surrounding nested tickets and the like. In a sane world, the above plan should be ok, but is either airline likely to object?

Any thoughts gratefully received.