Drink driving

I have been charged with drink driving after getting caught with my reverse light on about to drive home. My breath test was 57 milligrams. I have wrote a letter to present in court to show my remorsefulness and that I'm genuinely sorry for the crime I have committed. This is my first time ever in trouble with the law. I am suppose to join the Royal Navy in a few months but am now aware that the likelihood of that happening is very slim now. I was wondering if I need a solicitor in court even though I am going to plead guilty and if there's still a chance I can join the navy whilst still have the driving ban that I'm going to get.
You are not required to have a solicitor with you at court but it is helpful to have someone there to speak on your behalf and highlight the relevant mitigation and background to the offence.

A reading of 57µg of alcohol per 100ml of breath means you will be sentenced to a ban of between 12 and 16 months and will have a fine imposed. The fine is based on your income and starts at 150% of your 'relevant weekly income'.

This will also result in a criminal conviction which may have an impact on your application to join the Royal Navy but that is something you ill need to speak with the Navy directly about.
If I have wrote a letter for the judge to read that explains my mitigations will I just have to give it to them or read it out personally. Also will I get questioned about the night of the incident?
Buy CDT Test