Success Gentlemen!
I had the time to remove the fairings on the CBR today.
I used a piece of wood as a make shift stethoscope, and had a listen to the motor. The noise i could hear just wasn't coming from the motor.
On further inspection of the exhaust, the sound seemed to be coming from somewhere in the middle.
The collector pipe has a plate that splits the flow, the spot welds on the top and bottom have sheered (The exhaust is the lowest part on the bottom of the bike) and thus rattles when the engine is running, and gets worse with increasing RPM.
Just need to get a welder to stick this back in place.
Thanks for all the help
Cheers