Hi MANFOD.
I searched various dates in Nov/Dec/Jan, and I was definitely getting CPH at 12 weekly, like I say, it was 2 daily barring Thu/Sat which were 1 daily.
Basel does indeed have a couple of weeks at 3 weekly, but does seem to remain daily on the whole.
Keflavik should be interesting. It will be 16 weekly this winter with daily flights from Icelandair and Easyjet as well as 2 weekly Thomson. Can the route sustain that much capacity? I'm not 100% sure.