In reply to carrot_boy (North East Wales MC): Unfortunately the last time a passenger ferry from the UK docked in Bergen was during the eruption of Eyjafjallajökull. And that was only to pick up stranded air passengers.
The most straightforward method of getting to Bergen would be to take the Harwich to Esbjerg ferry, then drive up through Denmark to take the Hirtsjals - Bergen Ferry with Fjordline.
Beware though, at peak season it is ridiculously expensive and very crowded. Also if you go with this option make sure you are VERY accurate regarding the height & length of your vehicle as if you are too large for the car deck you will have to pay a huge amount to move to the cargo deck, with no possibility of negotiating. (I used to work at the docks in bergen and part of our contract was dealing with the ferry from Hirtsjals, so I know how expensive/strict/bad it can be)
Hope this has helped, Matt