Thanks for the reply mate. It looks like my WOE install was at fault rather than the terrain.
I had created my Wings Over Scandinavia install by copying over my Wings Over Ukraine install(Russia vs Ukraine with Turkey on the sidelines based on Pfunk's Black Sea terrain), renamed it Wings Over Scandinavia, and then started populating it with the appropriate planes and ground objects etc. and took out my Ukranian and Turkish stuff. So as an experiment I put North Cape into the Ukraine install and got the same problem. So then I tried North Cape in my NATO Fighters install and it was fine
Next I did a fresh WOE install, installed North Cape and that worked fine, so I copied my theatre specific stuff from Scandanavia and deleted that install leaving a new Wings Over Scandinavia install and all is good. Phew!
Just out of interest, does anyone rmember DiDs EF-2000? The controllers had Norweigan accents IIRC. I wonder if the sound files could be used in SF?