I hoped some of the jitter was traffic management but my jitter actually got measurably worse on the higher speed gamer package!
The traffic management does not apply to the downstream, only the upstream at 50Mbps... Even then the upload speed is 1.5Mbps which is plenty for gaming. So to all intents and purposes the traffic management should have made no difference. As others have stated it's just the way the virginmedia network is designed.
Companies such as TalkTalk and BT often have a worse reputation to the public than virginmedia, with people stating virginmedia is fibre optic and has better cabling etc... Reality is that for gaming you'd almost always be better with a TT or BT connection. Congestion as well seems much more rare on the other providers. I personally had virginmedia and could not believe how poor my connection was. I was paying 39 quid a month and my TT connection at 18 quid performed better for most tasks.