Newcastle to Bergen used to be 'the' one but it was taken off in the last few years and there's no direct ferry any more, as far as I know.
I looked into this a couple of years ago and found the best way was probably via Denmark (Esbjerg) but not sure if that even runs any longer. Harwich to hook of holland then up via Denmark?
I think wild camping is OK in Norway but take plenty of clothes and a good stash of your own ale, it's £10 for a beer over there!!
EDIT - yep, just looked on DFDS website
"Our Harwich-Esbjerg route sadly closed in September 2014. Although there is no longer a direct ferry route between the UK and Denmark, there are still a number of convenient ways to get to Scandinavia from the UK using our other routes."
(Being Calais or Newcastle to Amsterdam...)
"Our ports in Dunkirk and Calais are approximately 7 ½ hours’ drive from Denmark, via Belgium, Holland and Germany." (By modern standards, presumeably - so it'd add at least an extra entire day behind the wheel before you even get there.... :evil: )