I've just returned from JNB (Johannesburg) - DXB - SYD - DXB - JNB, so I don't have much to offer on the UK - DXB leg but here goes on the rest.
Emirates have 2 flights DXB - SYD one is a 777-300 the other A340-500. The 777 stops in Bangkok (BKK) for 1 hour to refuel and change crew. On the way to SYD you have to disembark, wait 40 mins and then reboard, but on the way back you may stay on the plane if you wish. The airbus flight is direct. I don't know when you are flying, but they are due to start the A380 on this route very soon.
As to the in flight entertainment system (ICE) only the newer versions have power & USB at each seat in economy (Yes, in economy!). As far as I as aware the USB port is to plug in ipods etc. and view/listen through the planes system.
If you go to the Emirates web site (
Emirates | Welcome to Emirates.com ), hold your mouse over "Flying with Emirates", click on "Services by Flight" you can then enter your flight no. and date of travel and check the services. If it mentions the ICE system you are out of luck, but if it mentions the "ICE Digital Widescreen" system then they should have power + USB.
Ask if you want any more info.
Cheers