Implement an electoral process for a new, permanent constituency that includes all registered UK overseas citizens. Allow these citizens to vote for a UK Overseas Citizens MP who will ultimately represent their interests on various issues, such as: taxation, travel, pensions, healthcare, etc.
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UK citizens living overseas are gradually disenfranchised from the parliamentary process as their time abroad increases. Though they may or may not plan to return one day, they are still UK citizens with rights conferred by, and obligations to, the United Kingdom.
Furthermore, vitally important matters of state, eg. referenda for EU membership, Scottish independence, etc, are so far-reaching that the right to vote should be permanently established for all UK citizens, wherever they may live.