Hi Dave,
I've just had a look at the diamond wheel as you suggested, by watching it as it slowed down, i tried two blades, one fairly new and the other well used, but recently sharpened using a sharpening block, and there is a very small amount of movement. But i'm not quite sure how much movement is ok !! I'm going to buy another blade, if the chipping continues, i reckon you could be right with it possibly being the spindle.
Thanks Brian