In GWX 2.1 I took my XXI through the Channel in summer of 1944 for her maiden voyage -- and obliterated a heavily escorted convoy along the way. I guess I was lucky I didn't hit a mine but the destroyers weren't any worse than normal. Of course a XXI with a nice assortment of homing torpedoes didn't hurt.
I also got way, way too near the east coast of England in a IXD2 the patrol before that, following a convoy report I received as I transited the North Sea out of Bergen. 15m/s wind and huge waves must make for poor sonar conditions in 40m of water, as I escaped (to my utter amazement). I think every square meter of the sea in a 10km radius got hedgehogged during that debacle. Just not (quite) at the exact same time I was occupying it
So late war Channel forays are survivable . . . if not exactly recommended.