First, Kal Maximus had similar issues in the
Wake torpedo thread. If you do not understand the procedure he did, you can try sending him a PM and see if he can make you a mini-mod to add on top of what you have.
Second, I don't remember for certain the way to do that, but can you get it to zoom with the <Tab> key?
Third, the English Channel is mined, so unless you take your time and do a lot of slow periscope searching, it is best to avoid using the Channel anymore... Take the long way home...