I just managed to retune mine. Not sure how I did it but I will try to explain.
On the actual TV there are a panel of buttons. if you press one of them (the one next to changing the AV etc) a message will come up about adjusting screen or slope (something like that). Use your controls and press OK, eventually it will start a digital retune which is different then if you try to do it from controls. After this it will do a normal TV retune and when all is finished you should have all your channels back.
I am sorry this isn't very clear, but I worked it out by chance (I was fed up with channel 5!). I don't want to risk ruining it to work out exactly how its done.
Good Luck xxx
Laura, March 2009