Thanks John, that is what I was thinking, thanks for comfirming that. I opened up the top part to see if the belt had slipped or something, but I can't see that voiding the warranty as it's a basic part of changing the RPM?
This is quite untimely, amongst several projects at the moment that all require some use of the mill. I've honestly hardly used it, so it's frustrating for it to just let me down right now :/