I am no expert but I don't think it is appropriate to brief a barrister for a Magistrate's Court hearing. The case is simple and does not require some expert to challenge the evidence or to interpret the law. The policeman is asserting that you were using a hand-held communication device, you say you weren't. Just go along and say exactly what happened. You haven't really told us all the facts. If you were pushing the button on a bluetooth earpiece - then you should be fine, but I don't understand why the policeman stopped you. If you were pushing buttons on a mobile phone - even if you were only enabling the bluetooth - then you will probably be found guilty. Whatever you do, do not criticise the court system or accuse the policeman of bias or of falsifying evidence in order to meet a quota, or of bad driving because he looked through the side window. That is not going to help - it is not relevant to the accusation and it sounds desperate.