Excessive belt noise when engine was really hot

[RedWings]

Got stuck in traffic yesterday for 3 hours (those who tried going on the M6 yesterday morning will have also felt the pain!) and although the car ran fine, stayed at the right temperature etc, the belts started making quite a loud noise - hard to describe but almost like a rattling/vibrating tin can..sort of. When I got back in the car later in the day (engine back to cold again) the noise went away. Doesn't seem like anything to worry about immediately, car is due service and first MOT just after Christmas so I was *thinking* of waiting until then and getting it looked at by Monkfish at the same time...unless it's actually more urgent than that?! :O

[NickBv8]

I get exactly the same noise,but mine is when the engine is cold and maybe a little damp.Lasts about 5 minutes the gradually goes away.
Never happens in the warmer weather.