zombie84 said:

Carrie Fisher went though, even though she had no scenes. She just wanted to hang out.

Carrie Fisher visited some friends in Sweden before she went to Norway, so she had a reason to be in that part of the world besides shooting Star Wars.

I also think that it is possible that they had planned to shoot scenes with Carrie Fisher but had to cancel. After she had arrived in Finse, she soon fell ill and spent most of her time in her hotel room ... They also experienced a heavy storm that severely influenced the shooting schedule. They shot the scene with Luke in the storm escaping from the Wampa's cave then because it was the only scene that they could shoot at the time.

skyjedi2005 said:

So the picture with him visiting the set with Mark and Carrie in winter gear must be at elstree then.

Must be nice to wear winter jackets under those hot lights.

Only the exterior shots were shot in Finse, except for the shot of Mark Hamill sitting in his X-wing about to take off, which was shot at Elstree with only sky as the background.

Are you thinking of the crew jackets? The crew jackets were worn everywhere, including indoors at Elstree, etc.