Bump stop squeak would be just that rather than springlates - not connected other than the springplates lowered it enough to sit on stops. I think maybe you don't have rubber stops (you haven't said) and that explains the banging + springplates are creaking. Some under pics would help...
You may have guessed already that I am not a mechanic Went down the IT route.....boring !! Anyway. Correct there are no bump stops on the rear. Rear shocks are not all that compressed. Measure 400mm from bolt to bolt, sitting on drive. KYB gas-a-just measure 424mm fully extended. So ok there, and they still have about 5" or 128mm of travel in them. Not measured them fully loaded. I am sure the creaking is from the spring plate, and I now think after having a good look underneath that the knocking noise is my csp exhaust backbox hitting the lower bolt of the shock absorber. It is already resting on it, so when I hit a bump, it is moving off and banging back. I am sure that is it. I'll try and take a pic thanks for all your reply's