Thanks for the tips. When the noise occurs it seems to have a very rhythmic muffled "beat" to it that coincides with the belt manufacturers marking rounding the alternator pulley. To my ear it has no metallic ring, squeal or rattle that you might expect from a dodgy bearing - and it is...
Seem to have intermittent strange noises from the region of the auxiliary belt. Car is fitted with working aircon and belt tension seems OK but often on start-up get a fairly loud repetitive noise from the belt area. Does not always happen and stops after a short time. Obviously cheap and...