The survivors would probably end up in Jutland or Norway, maybe Sweden due to the currents.
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The main wind pattern is also western, but with prevailing eastern winds, they might end up in Scotland, depending on the vessel. The Jutlandic coast has experienced a large number of shipwrecks in the past.
Even if a boat gets out on the open ocean, the Gulf stream flows northeast, so there are very small chances to get to Sub-Saharan Africa.
So the answer would be: (a), very small but depending on the survivors' ability to navigate and the wind direction. (b) None.
Here is a sad account of the North Sea currents