It doesn't matter who you fly with. Economy is economy, and leg room will be cramped.
I flew with Singapore Airlines on the Airbus A380, and found it to be cramped, and I'm only 5'8''
Haha, I can assure you that the Singapore A380 is far less cramped than a lot of other carriers/aircraft types. The 777-200s in particular have been responsible for some very near mid flight rage incidents from myself

My vote is for Singapore Airlines and the A380. Best I've used, and I fly the London - Sydney route pretty often. The Airbus seems to have a fair bit extra room on the window seats between passenger and the wall/window, which is nice. Plus theres loads of room to go for a walk - climb some stairs, should the feeling take you!
