alosso:
OTOH, the UK is the body covering the three others plus Northern Ireland, whether they like it or not.
Now, let the chastisement begin.
No need for that:)...A worthwhile point of order:
The British Isle is a commonly accepted geographical area.
The UK is a formal political union. This is not though the place to open up which parts of what want in, and which parts of what would prefer out.
Then (not least) there are the Crown Dependencies which govern themselves, and have their own parliament which is why they are not represented in the UK (London) Parliament. The Crown is distinct from the overall Constitution (parliament chopped the Kings Head off remember). These dependencies are however afforded protection and such by the Crown. They are not overseas territories, but I will leave that bit alone.
EDIT: Should have also referred to the Commonwealth. This is a much loser arrangement for these high level purposes, but it is distinct from any of the above (mostly).
Basically people want their own flag why not?