Engine Knocking Noise

Hi all, first question on here :smile:
I'm experiencing a knocking noise coming from the engine that I'd initially diagnosed as stuffed engine mounts. First, I replaced the top mount (driver's side attached to the torque arm). The noise seemed to have disappeared for a short while, but began to return over the following days / weeks. The replaced mounting had all but collapsed - so it was a worthwhile replacement even though it didn't solve my problem.

The noise seemed to be occurring most when lifting off of the clutch - particularly at low revs. And it's was more evident when the car was cold. It occurred (and still continues to) knock whenever there's light torque on the engine - when gearing down for a slow turn, for example. My next step was to replace the gearbox mount (which had slight cracks). Again, the knock disappeared for a few days and began to resurface.

Any ideas what else it could be. Would the remaining mount (side mount - not always sure what you guys up in the UK call components :wink:) cause this kind of knock? Or could it be suspension related? The engine does seem to move ever so slightly when moving over rough terrain and certain bumps (or I imagine it does).

Any help would be massively appreciated.

Thanks. And awesome forum btw