I have looked at many options, and the essential part of the journey is from Harwich to Esbjerg on the DFSD ferry, (West coast Denmark) on DSDS.
From there there are options.
Drive from the DFDS ferry terminal all the way to Oslo.
Or Drive from the DFDS ferry terminal to Hirtshalls, the northern tip of Denmark, 345km, taking 4 hours.
Take the ferry from Hirtshalls to Larvik, 3,75 hours.
Drive from Larvik to Oslo, 144km taking 2 hours.
The ferry cost is Euro114 weekday, Euro 131 weekend.
Total time takes an estimated 11,75 hours, wich has a 1 hour built in for arrival time at the Hirtshalls Color line ferry terminal.

The alternative route, is probably my favourite.
Disembark at Esbjerg, and drive across Denmark.
First toll is Euro30 for the crossing to the island Storebælt, then the second toll Euro 38 for the Øresund tunnel / bridge from Denmark to Malmo, Sweden.
The drive from Malmo to Oslo is a very easy E6 north all the way. 570km, taking 7,5 hours.

Total travel time with using the Color line ferry is about 11,75 hours.
Total travel time to drive the bridges, without the color line ferry, (my choice) takes 11.25 hours.

You would save aprox. Euro 63 doing the drive, but that would have to cover the additional 418km that you would have to drive, as opposed to taking the ferry.

Having weighed it all up, I prefer to take the bridges and tunnels option. Just for my enjoyment of seeing beautifull bridges.
As there is the Esbjerg to Harwich ferry to take anyway, for the 'ferry freaks'

Good info. and prices here for the 2 x tolls.

Toll Bridges in Denmark - Denmark - VisitDenmark: The official guide to Denmark with Danish tourism and travel information such as hotels, map, flag, copenhagen info etc.


'vette

ps.

For the one's of you looking to drive the west coast of Norway, then instead of getting the Color line ferry from Hirtshalls to Larvik, take the Color line ferry from Hirtshalls to Kristiansands, then follow the coast road.

Alternativly, if you do take the Oslo route from Sweden, then it is also a beautiful drive from Oslo to Bergen or Stavanger, then simply head north for as long as your hearts delight.

There are also ferries from Fredrikshavn (DK) to Gothenburg (S) and Oslo, these are the ones I would choose from Oslo. Gothenburg - Malmö is an incredibly flat, long and boring ride...

There is also the posibility of taking the fjorline ferry from Hirtshals (north in denmark) to stavanger on the south west coast of Norway. It takes about 11,5 hrs. and you don't need a cabin and it's not to expensive if you book well in advance. Only problem is that you arive during the night in stavanger...