rear knocking/vibration

Hope someone can enlighten me because this has been annoying me for a while now.

when i go over speed bumps i get a knock at the rear, seems to be more passenger side. Also when i have a car full or someone sat at rear passenger side i get a vibration when stopped on idle, if i rev the engine the vibration goes.

The rear shocks were new last january, had rear axle bushes checked and they are fine, checked around exhaust and cant see anywhere it can be knocking against. So really am struggling to narrow down the culprit, only thing i can think of now is rear top mounts but can these cause the knocks and vibrations?