Please Help

I have recently had the O/S cv joint and brake disc and pads replaced to cure what I thought was a metallic knocking noise when on  a bumpy road, it stops when foot brake applied and restarts when released,   I could hold the driveshaft and move it in and out to hear it knocking onto what I thought was rear or brake rotor, after cv job its still doing it..

. any ideas greatly appreciated,

If it stops when you apply the brake that indicates it must be related to the braking system so that's where I would start. Make sure nothing is lose etc.