flights
from edinburgh, better choice of flights, not to expensive, actually pretty cheap if you get in early and fly to Oslo proper.
not sure about the riding round oslo (it ain't too hilly) but using a train you should have plenty of choice. But unless you need to be in Oslo would suggest getting the train up to and staying around Lillehammer.
trains
you should also be able to get cabins up there no prob, though doubt it will keep costs down.
bikepark
june or july actually it's august there is also a mega race about lillehammer 90 or 100km in a straight line pretty much, think about 12,000 folk enter but sells out reet quick. Can't remember the name though