[closewith]

Even then, the Channel Island are a Crown Dependency and use the GB ISO code, while the Isle of Man is also a Crown Dependency and has its own ISO code.

The British Indian Ocean Territory and the British Antarctic Territory are both British Overseas Territories, but unlike the Falklands, Bermuda, etc, do not have their own ISO codes.

So the determination is more complex than that.

[Symbiote]

These have codes GG, JE, IO.

Claims of Antarctic territory aren't recognised internationally, so the codes were removed, but it used to have the code BQ.