Hi Paul,

It's very difficult to diagnose such a thing from afar, so it's best that you take the car to a mechanic to have it looked at, especially if the noise is indeed coming from the timing belt area. If it's from the auxiliary belt, then there may be something stuck on the belt or it may be damaged. The noise probably goes away as the speed increases. Also bear in mind that noises sometimes seem to come from one area of a car when in fact they come from another. This could simply be a pebble stuck in the brakes, for example. 

Either way, safest thing to do is to bring the car to a good mechanic to sort it out.