Holding northern Norway after 1940

What if Britain held northern Norway from Trondheim north after 1940?

It creates a costly northern front for Germany and materially changes Atlantic and Arctic naval options.

A viable Allied enclave would need to hold the Norwegian coast from Trondheim northward, with a free Norwegian government and army operating from the region. Control of Narvik threatens Swedish iron-ore exports and denies Germany fish-oil facilities and easy movement along the full coast. Coastal aircraft, radar, fighters, and motor torpedo boats would create a continuing attritional front while narrowing German Atlantic and Arctic-convoy options. Sweden would face intense pressure from both sides, and Germany would have to supply another front while campaigning in France and perhaps the Soviet Union. British Marines and Norwegian forces would need to consolidate Narvik and Trondheim quickly, requiring a stronger initial campaign than history.