I'm having the same issue mate, pretty alarming wobble when going over larger bumps in excess of 40mph.... mostly on motorways, going over a rolling bump in the road etc - car dips after the bump as normal, but wobbles left to right when rebounding...this happens on straights, corners wherever, but isn't present when goin less than 40mph...
Could it be shocks, sway bar, drop links? Did you ever resolve this issue mate?