This is a very good question. The notion of work is that it is for "hire and reward", i.e, employment. So the answer is no. But you are travelling to and from a place of work, so the answer is yes. On the bounds of probability, what viewpoint would the insurer adopt? In short, notify your insurer of the 'charitable work' you are carrying out as magistrate to ensure you have adequate cover in place. It is always best to avoid allowing an insurer any opportunity to not pay out in the event of a claim.