The more I think about it Chris...the more I reckon my belt was just a bit crappy when I got.
My whole kit had a few defects, like the sonic weld failing on the pulley, the manual has incorrect pictures in it (which I told Chazz about - he was actaully pleased I pointed it out) and now this.
Maybe if I just put the 3213 belt on it will all be ok.
Escuse my crude drawing, but is that what the idler bar looks like with both pulleys attached as you have said?
Cheers Chris.