Replacing my NOX sensor did the trick as far as intermittent power loss was concerned and as described mine got worse the longer it went on.
The cambelt/tensioner failure was unrelated. By the way my car getting new engine today, having clutch done while in there as will only have to pay parts as they will have it apart anyway. It's gonna cost me £3.5k all in, rubbish!
My opinion is that the Audi is a very nice car and I would recommend it to anyone BUT only buy the car from new, sell or part exchange the car before you exceed the warranty conditions. If you anyone chooses not to take this advice please at least completely ignore Audi guidelines on servicing and maintenance as they are not worth the paper they are written on. If you own a 2.0fsi engine get the cambelt and tensioner checked when you hit 60k miles or risk losing your engine (and a lot of pennies!)
Sorry for sounding so bitter just hate having to spend money especially so soon after Christmas!