Stopover is not such a bad thing on such a long (4 hop) journey. Is the stopover on the way there or the way back? If it does bother you though have you considered a couple of alternatives:
- Only travelling to (or from) LHR on the leg with the long stopover and taking the train to MAN (bearing in mind the MAN flight goes via Munich anyway,which adds time) . With this should be able do MAN on the other leg.
- Purchasing separate tickets CFS-SYD and SYD-MAN to see if that eliminates the long stopover (of course allowing plenty of time between the flights on the different tickets).

I guess too late if you have already booked and ticketed your flights.