Have a look a http://www.hurtigruten.co.uk/. Not exactly a cruise ship but many use it as such. It is basically a local ferry that runs all the way up the Norwegian coast.
NCL seems like the ideal line for you - freestyle dining - eat when and where you want. No need to participate in formal nights if you do not wish to. And the ships are fantastic [the newer ones.
I believe Thomson cruises do the Fjords and the Celebration will be the ship- not a bad ship, no surcharge to eat informally- you can eat in either the waiter service dining room- The Meridian and usually can get a table on your own, or eat in the Lido restaurant- buffet. Not exactly a luxury ship like the more ridiculously expensive ones but a nice ship and you will have wonderful servic.
We have not long come back from the Fjords with Thomson Cruises, we had a smashing time, quite budget, but you get well looked after and its chap and cheerful. The ports are quite small, but they are stunning. All I kenp saying was if there is a god and heaven this must be it. Well worth a visit, you will enjoy the fresh air and the stunning scenery. good luc.