[3Jane]

I always used the Channel until I was transfered from Willhelmshaven to Lorient. Stay 3000 metres off Calais, far enough out to avoid the mines and being spotted by the armed trawlers in the port and close enough inshore to miss the others further out. Run decks awash (7m) in the full dark, whilst the French coast is still hostile. After that when it is in German hands, still transit at night but you can now do it fully surfaced. If you calculate you arrival time off Calais right, you can make it through well before dawn. Then silent running through the daylight hours sticking to the south of the channel. Not too close inshore where it is too shallow. You will probably get contact reports showing convoys in the channel, but I alwas ignore them. It's way too shallow for that kind of thing.
I would wait until the last minute before exiting your mission, the weather might turn bad and the destroyers could loose their fix on you, if your very lucky. A quick heroic surface dash in the dark might pull it off, or not. Never mind about the dead crew, as soon as you surface just toss them overboard like dead mackerel.:p