Lane hugging and brake checking

Sorry if this is the wrong place. I've just received a letter from York police saying I was doing the above. There's images of me in the middle lane just driving. Short story is, I had cruise control (radar CC with auto braking) on and I was just chilling, totally forgot I was in the middle lane and there was nobody else in front or behind and I wasn't speeding. Hold my hands up, I'm guilty. What am I looking at here? A fine? 3 points? First time I've ever been caught doing this.