Nae good Rob, cannot think of any full proof way other than getting you hands on this with the DP off.
New alternator arrived today, the new one is silent when you spin the pulley, the old one sounds like the bearings have gone, definately doesn't sound right, doesn't spin freely either, feels and sounds like there is heavy friction. Won't know it's 100% fixed until I drive it but it should be now (fingers crossed).