I have an Australian 7R, and I get what I think you're describing.
For me it feels like a wheel is out of balance sometimes, but not all the time. It feels a bit like you're driving over tiny bumps in the road even on a perfectly flat highway. It can only be felt though the floor/feet/seat, and for me is not felt through the steering wheel. The vibration does not get faster with speed and seems somewhat random.
I've been back to VW numerous times and they have not been able to solve it, and when comparing back to back with a brand new R it has the same characteristics but mine just feels 3 times worse. I've tried re-balancing wheels, rotating wheels, different tyre pressures, then brand new tyres, and even swapping wheels/tyres with a brand new golf in the dealership.
I've essentially given up and decided I can live with it. But it's the one thing that annoys me about this car, but the funny thing is that passengers can't really feel it so I think i'm just uber sensitive to this now, but the tech at VW could feel it too and tried very hard to find the issue, and couldn't, but didn't seem willing to start replacing parts like bushes and struts in a blind attempt at finding the problem.
Let me know if you ever find a solution, because I would be immensely grateful.