There are not so many cars in Northern Europe, but that makes it nicer to hitchhike if you don't mind walking.
You can legally pitch your tent almost anywhere outside of cities. But remember, the winter can be extremely cold and dark in Northern Europe. Choose a country for more specific information.
Countries
Denmark, Estonia, Finland, Iceland, Ireland, Latvia, Lithuania, Norway, Sweden, United Kingdom of Great Britain and Northern Ireland
Autonomic Islands or Regions
Åland Islands, Channel Islands, Faeroe Islands, Guernsey, Isle of Man, Jersey, Svalbard and Jan Mayen Islands