Letters dont do jack shit unless there is some loop hole or ridiculous circumstances or you have a perfectly spotless record for atleast 10 years. Trust me. I've written in twice, once for being booked for f**king fog lights when it had been raining and there was patches of fog about and the f**king cock sucker cop went ballistic at me and i was 100% respectful the whole time. Wanker. Makes it worse i wasnt even sure how to turn them off/on it wasnt intentional it was a brand new XR6 several years ago. Hope that *&% rots in hell.
Go to court, dress respectfully, and explain exactly what happened. It is a massive advantage to take a lawyer but really unless your fighting to keep your licence i wouldnt bother. But if you want to fight it absolutely go to court. I was in a car with 3 other people and we got RBT'd by the cops, all pissed as a fiddle and the driver decided to try and get home instead of just moving the car somewhere quiet. I cant remember what he blew, but it was enough for automatic loss of licence - i did the test aswell to see if i could drive to move the car. He does handle his grog really well like myself so was reasonably safe to drive considering it was 3am on a week day but thats no excuse for being stupid and anyway he went to court, a mate's dad is a barrister or something and went with him, he got off thankfully did have a good record and representation and got to keep his licence and just has to keep a clean slate for 1 year or something and thats it. So the law can be fare sometimes.