How much disclosure do you think is required in a speeding case? You don’t say how you were caught, which will have a bearing on the evidence that will be produced.
I’m not sure “nothing to lose” is correct. If you plead guilty, you will receive points, a fine (reduced by 1/3 for the early guilty plea), a small costs award and surcharge (based on the fine).
If you are convicted after trial, the fine will not be reduced by 1/3, so the surcharge will go up, and costs start at £650-ish. You’re essentially risking an extra grand (thereabouts) by pleading not guilty with no defence.