I noticed you didn't mention Hong Kong's or Malaysia's very large populations
No reason to at all. Every reason to mention those countries with a tiny population who chose to leave later for obvious reasons.
HK constituted more than 10% of Great Britain's population
Hong Kong was never part of Great Britain (or the U.K.) and was handed back the day the lease ended, though most of the population wish it had never gone to China and many have since left due to your ally's human rights abuses.
Also, why does it matter what Antigua's or Barbados' or Guyana's population was?
Because the smaller colonies tended to want to stay longer due to the difficulty of sustaining themselves economically as a state. Some have chosen to remain for that reason.
Is not the principle of self determination universal?
Hugely so, however r*SSia has never grasped that. Hence their illegal and unprovoked invasion of a foreign country and their demagogues' ridiculous false claims on the Baltic States.
However you are trying to deflect from the issue.