Norwegian are big enough to have made a major impact at LGW, there is nothing to say they could not do as well if not better at MAN. I thought they would be the next Aer Lingus, the truth is they're that rarest of things. Something properly new in the market.
However they are over extending themselves and I think they understand that. People will book anyone offering the right frequency and value via any of the usual websites nowadays.
I appear to have a smiley attached to my post. I don't know why!