Realistic (with maximum wankery) "Nazi Win" scenarios are the Nazis having all of central and eastern Europe. The Wallies are never going to accept Germany annexation of France, much less actual British territory. And there is no scenario outside of ASBs in which the Nazis can actually defeat as in completely neutralize Britain, which is what would be required for stuff like the Channel Islands to be conceded.
So a white peace will be signed where Britain and France recognize Germany's gains in eastern and central europe, the nazis will leave the islands, they will go back to Britain and that will be the end of it. In fact, if I recall, the channel island occupiers, believing the war would quickly end in a German victory, were prepared to leave soon, which is also why there was not (early in the occupation) a lot of animosity between the occupiers and the occupied, as it was expected this would be a short term thing.