Ive had a slight problem with bandmin recently, it use to create results that were only slighly higher than what cpanel & WHM produced, but now for 2 sites its reporting twice as much bandwidth usage as cpanel, is bandmin always right?

CPanel only keeps track of HTTP usage.

Yes but the sites that have the difference dont have any other kind of traffic except for a small amount of incoming ftp traffic.

E-mail pwebtech and they have an MRTG installed which will show you your bandwidth usage.