I've run the channel many times myself... I just stay close in to shore along France and run silent as enemy shipping appears.
On a side note, I don't remember which exact port it was (I'm at work now and therefore don't have the map handy), but along the southern side of England when running the channel, I decided once to take a chance and check out an English sea port for targets. Oh My God! There were 20+ C2 cargo ships at anchor there! I had a FIELD day sinking them! Got 13 of them with Torps and deck gun until a destroyer FINALLY showed up. But he was really miffed at me! I finally escaped him by crawling between the remaining C2's and working my way slowly South once I was clear of them.
Running the channel can be fun! Just take your time and keep a sharp lookout.
S