I'm on my first campaign and have GWX installed, am up to September 1940.
I spotted an aircraft once each during my first 2 war time patrols.
I think it was my 4th or 5th patrol where I spotted aircraft 5 or 6 times and was attacked 3 times IIRC. This was SW of Scapa and down the Scots coast. Luckily I had enough warning and was able to dive away each time and avoid their eggs.
Since then it's been quiet.
These are all North Sea patrols along the British east coast in my IIA U-6

-kwm