Hi all, just thought this may be of help to someone. We have a 360 box and the hard drive started to play up (lost all recordings, freezing, time shift erratic etc) so after getting the runaround from the call center telling me to do totally unrelated stuff like "stick a pin in your routers reset hole" and similar stuff they arranged for an engineer to call. The engineer agreed with my suspicions that the HDD was indeed faulty so a new box was sent out. On recieving the new box I followed all the instructions to the letter but the new box wouldn't even show a welcome screen. It just kept rebooting and showing a blank screen for hours. Another call to 150 ensued and the same "have you tried rebooting it?" Or "are you sure the cable is plugged in?" No luck whatsoever with this so I plugged the old faulty box back in so we could at least watch TV. An engineer contacted me and sent me another new box today which had the same issues when I tried to install it. No picture black screen and no welcome page on startup.
Obviously it near impossible to have 2 boxes with the exact same fault so I plugged the new 360 into an old tv and lo and behold it booted correctly first time.
It looks like 'out of the box' the 360 was outputting a signal on first boot that couldn't be read by my main TV (3 year old hisense) but could be read with no trouble by my scummy old 24inch TV (same hdmi cable)
As soon as the boot, installation and updates were out of the way I plugged the 360 back into the hisense and it's working with absolutely no problems.
So just a word of warning if you have a new 360 and it seems DOA try another TV first and save yourself hours of call center shenanigans. (is there a direct number to call for proper tech support because the call center I spoke to on both occasions were really poor on the technical side of things.)