If the police didn't submit, whilst pulled over, a traffic offence report and sent that off to Sidcup DA15 0BQ (Met Police Camera and Prosecution Centre)... then really and truly it was just a warning. I've been pulled over after doing some speeds at night, and they said 'letter's in the post, don't ignore it' and as far as I'm aware, that is just an empty threat.
Don't quote me on this, this is just my experience. Also, if they did send a TOR, they have 6 months to issue you a NIP to your address otherwise it's unenforceable.