I've done it the opposite way plenty of times. Drove my Escos to Ford Fair in 2008 for example. Ferry from Harwich to Esbjerg is one option cutting down on the miles, but its expensive. Go on Google maps and use the route planner, gives you an idea of distance. If you're driving all the way from England via France, Belgium, Holland, Germany, Denmark, Sweden then into Norway you're most likely looking at closer to 1500 miles one way.
I think, if I was to do it, Id drive the fully length one way and ferry the other.
I think fuel price work out about the same as her for France, Germany and Holland, but what's it like in Denmark, Sweden and Norway? would the best way to work it out be use UK prices? what would be a sensible amount of days to do the drive, with a def over night stay in ADam?