I'm having a similar issue bud. Replaced my top engine mount and gearbox mount (both of which showed signs of wear). Initially the problem appeared to have been sorted, but the knocking noise reappeared over the next few days. Trying to figure this out as well.
Edit: Realise what you're talking about with the stabiliser bar I think, Paul (was asking which one it is).
Another silly question. What's the difference between the gearbox stabiliser bar and the gearbox mount. Or am I being daft?