I've been looking at Norway myself this year or next. The only direct sailing is on a freight boat from Immingham (near Hull) to Brevik (south of Oslo). This goes only twice per week, takes well over 24 hours and when I got a quote for just me and the bike, cost over £500 (I think it was £512 - meals included). With all the freight sailings they can change your sailing at short notice as priority is of course given to freight:
http://freight.dfdsseaways.com/dfds_ferries/north_sea_ferries/
As on the above page there are more frequent freight sailings to Esbjerg and Gothenburg from Immingham. I haven't looked at the prices for freight boats to Esbjerg (from Immingham or Harwich) but I believe the Gothenburg ship is a similar cost to Brevik.
On a passenger ferry you can sail from Harwich to Esbjerg in Denmark (around £350 return for bike and rider, cabin included). You can then get a sailing from Hirtshals in the far north of Denmark to Norway - these are frequent and not too costly.
The other option I have considered is to sail to the Netherlands and either ride up through Denmark to Hirtshals, or to Kiel (northern Germany) where sailings go to either Norway or Gothenburg (Gothenburg sailing much cheaper via Stenaline).
I've still not booked though - waiting to see what happens with my work situation before spending out. Hope that's of some help!