Seeing as they're replacing the entire fleet with these two types, I'm guessing there won't be any dedicated intercity spec stock for the Norwich services? In that case I hope these Aventras have some kind of 350/1 style intercity spec interior.
Why not? You can have different specs within the different classes easily enough (the 350s being a prime example!) so I can easily see an Aventra sub-class which is dedicated for the Norwich intercity services and with the interior to match.