Your challenge, should you choose to accept it, is to have a surviving Scandinavian language somewhere in the British Isles, with these rules
-The POD must be after the reign of Alfred the Great
-The language must have over 20,000 speakers
-The language, or its attached ethnic group, must be the focus of some regional autonomy/separtist movement of some kind (doesn't have to be very big, or have a wide following, but the language has to produce enough of an ethnic identity for the concept to exist)