March 2008 is still too far away to be able to book this. If you just want to visit these cities without any additional objectives (mileage earning and such), then you could do a DONE4 RTW:

LHR-PVG-HKG-MEL-PER-SYD-JFK-LHR

I suspect this will be cheaper than buying a non-RTW ticket, but it does force you to go back to London the long way round.

I've generally been disappointed with the service in Australian hotels, but the Park Hyatt in Melbourne was OK. Not great, but OK.