I haven't used mine in anger yet, still on 19 miles in the garage, but, I've experimented and the RDMS is easily turned off.
If you hit the button down by your right knee the 3 main systems are shown in the speedo panel, in green. Each one can be selected in turn and turned off via the steering wheel left side controls.
When I return home from Reading, early Sunday mornings, before first sparrows, I'm often the only car on the road. There are a few 2 or 3 lane dual carriageway 'S' sections where I safely cut both corners and the last thing I want is the steering wheel to try to wobble me round the S between the lines.