hi i have a good bit of experience with this. IF he was on a bike in the city he is TRAFFIC CORP which means 90% will follow this up. What i understand from this is you went from left lane over to the right lane to make a right hand turn. So you got pulled he prob cautioned you under a section road traffic act 51a,b or c. as well as driving without a full lienced driver that i would not worry to much about. he is going to get you on something. no point in worrying just wait till you get more info by post and contact a solictor it will be a day in court and your legal fees should be no more than 150e and a fine on the day do not get a barristor 3ooe min and complete overkill for a simple road traffic case