A correction here for O’Callaghan: Crown dependency is the correct term for the Isle of Man and the Channel Islands.
They are not represented in the Westminster Parliament, but fall directly under the Queen.
The Isle of Man has its own parliament, the Tynwald, the world’s oldest existing legislature. The Tynwald is made up of the House of Keys and the Legislative Council.
The Channel Islands comprise two bailiwicks, Jersey and Guernsey. Its legislatures are called the States of Jersey and the States of Guernsey.
Sark and Alderney both fall under the Bailiwick of Guernsey.
When Westminster proposed privatising the Post Office in the 1970s, the States (of both bailiwicks) and the Tynwald disagreed, and were allowed to form their own postal services separate from Royal Mail.
This is why these islands then ceased issuing regional postage stamps (bearing the Queen’s head but no country inscription) and instead issued their own stamps, inscribed Isle of Man, Jersey and Guernsey.
Stamps have occasionally also been issued for Alderney by the Guernsey Post Office.
Private issues of locally valid stamps have been made for Herm island (also part of Guernsey), but these have had no official or international recognition.
During the Second World War, the Channel Islands were the only British soil to be occupied by Nazi German forces.
With permission from King George VI, the island authorities issued their own postage stamps during that time.
Regards,
Mike