Have a look at these SAS offers to Scandinavia through Opodo who recently won a travel industry survey for most usable site:
Stockholm £104, Copenhagen £114, Oslo £122, Helsinki £170
Not the most amazing prices I hear you cry. True but we have had a look through and the availability is very good. When we checked it was still possible to book the May bank holiday weekend at these prices.
As always, it is wise to compare with other airlines and make sure you are comparing the total cost of the trip including travel from your home.