Hmmm. the USA were once British Colonies. Should we therefore append England to their addresses? Unlike the USA, the IoM has never been a British Colony.

I doubt you consider Wales, Scotland and Ireland to be part of England.

In Queen Victoria's time residents of the above and many other places would be considered Subjects of the Queen which is only a reflection on who was the Head of State.

If you have an official birth certificate that states Isle of Man, England, I'm sure many on the board would like to see a copy.