I had this going on for weeks. It is not the fact that the valve is meant to be missing, its the fact that the rear brakes are not efficient enough to pass, which is then put down to the Cup not having the load valve. I Spoke to Renault UK and sent them a long letter like they requested (I never got a reply to it). They refused to acknowledge there was a problem, even though my rear brakes were not efficient enough to pass its MOT. I even got VOSA involved to get some sense from Renault.
You want to know the outcome.....
Put people in the back of the car when testing the rear brakes. Some fix that is. In other words when I am driving without people in the back of my car, my rear brakes are not good enough to pass a standard safety test.