Start a career in Wilhelmshaven in 1939 and rush through the channel before hostilities break out. This should get you through the Channel just in time. Then go to Portsmouth. You can get there soon after the start of war. HMS Hood is there and if you position correctly you can sink it there and then.
The harbour itself is only mildly defended.
It was like this in GWX...don't know about GWX 2.0
__________________
Daddy cool 
|