Hello Andy Bell,
Thanks for posting your question in the Microsoft Q&A forum.
Azure OpenAI does support UK South, but access to that region depends on your subscription being allow listed. If UK South doesn’t appear and you only see Global it means your subscription has not been enabled for that region yet. There is no self-service toggle to turn it on.
To get UK South enabled, you must submit the Azure OpenAI access/update request form and also open an Azure support ticket asking Microsoft to allow list your subscription for Azure OpenAI in UK South due to your UK only data residency and public sector requirements.
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