I would take a stove if I were camping. If you're staying at hostels, BBs or - gasp - hotels, you won't have that much use for it.
And if by Northern Europe you mean northern parts of Norway, Sweden or Finland, camping is a good idea. At least as a backup plan. Stealth camping is legal here and there might not be any other accommodation available (within a reasonable distance). Same goes for places to eat.
--J