That's a big ditto for me. I never take the Channel route. First of all, there are usually a lot of solo ships north of England that you can shoot at. Second, the Channel is too shallow and dangerous for me.
I don't convert knots to meters. I use the method at
http://www.subsim.com/radioroom/show...light=tutorial to intercept and sink ships.
There's a four-bearing method floating around too, but I only use that in bad weather by hydrophone.