Appology to court - letter of mitigation

I am due in court for drink driving in a couple of weeks - no question of pleading anything but guilty with breath at 90+. Research so far indicates that it might be useful to offer a letter of mitigation highlighting one's personal circumstances, remorse and intended strategies to avoid further offending; but I can not find any clear account of the process: do I post it to the court; hand it to someone employed by the court and address it to 'The Magistrate'? The process seems a bit vague? any tips appreciated.
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