Thanks for the thoughts...
It's only November '39, so I've got plenty of time to get up to Norway, and I've been lucky enough in previous careers to have encountered BB's, so I'm leaning towards going for the merchants. I'm in a near ideal position, but the proximity of a number of escorts is starting to get me worried, so I might just try and put a torpedo in each of the 4 soft targets to slow them down (and hopefully sink one or two), use the reload time to evade (again, hopefully!) and come around for a second pass to finish them off. If I've got the time I'll get a shot off at the BB, and cross all my appendages that I get a magazine hit
Wish me luck, I'm going in!!