I go there frequently and one option for you would be to SYD to JFK (or MIA) to CDG and then take the TGV from CDG direct to Cannes which is a couple of hours and quite pleasant to train it. Otherwise, as everyone noted, you're stuck connecting through LHR (sigh) and with the winter weather you're probably dealing with bussing between terminals and then hanging for the flight to NCE, and then you have to train it (very easy and cheap) or cab it to Cannes. I wouldn't rent a car, parking is pricey and a pain in Cannes....unless you can expense it. Then who cares I guess. Trois Portes is better food than the usual tourist traps...if you're looking for food too.