In reply to Cellinski:
We've been living in Oslo for the last year, so have explored a fair amount of the south.
I'd consider a route that went like:
Bohusland: wonderful, single and multi (that is, two) pitch on granite that wants to be grit.
Oslo: some local crags - Hauktjern and Kolsås are the best two, both have a mix of sport and trad although only Kolsås is multi-pitch. Probably not worth a detour for, but if you're in Oslo anyway quite fun.
Drammen: some good climbing, sport and trad, about 45 mins east of Oslo. Single or two pitch I think.
Nissedal: trad and proper multipitch, Hægefjell is a dome of rock all alone, 10 pitches for the longer routes. Sport and trad.
Setesdal: single and multipitch, Bø has sport up to about 13 pitches if I remember correctly. Mostly sport I think.
Rogaland: sport and trad, some wonderful climbing. Single and shorter multipitch.
At this point you'll be on the west coast, you could go north to Usekdal, I've never been here but people rave about it so I should probably mention it to you!
Otherwise south to Kristiansand - not been here either I'm afraid (been out with injury this year) but the new guidebook just came out.
You could do the above and then on the way back cut the corner by getting the ferry back to Denmark from Kristiansand, save quite a bit of driving.
Campsites for motorhomes are fairly easy to find, it's quite popular.