It sounds like there's a leak in the system. The noise could be because the powerfluid pump has ran dry. Definitely worth looking for any areas where it's leaked from.
I'd recommend a diagnostic check to see if any fault codes flag up.
Have you tried the spare key? I ask as that can help narrow down the issue. If both keys are working then the key isn't the culprit.
I agree with Gareth, get this booked in at main dealer as it's under warranty. That way if there is an oil consumption issue Audi try and get out of at least nyiu can show it's been in before.
The E10 fuel is a nightmare. I'm convinced it's designed to kill cars deliberately. Let's face it it can't be for emissions like they claim because all cars get less mpg now!