Well...
Tested it again yesterday morning and on the way home and again this morning on the way in to work, as I thought the car being cold might have something to do with it (on the way home the car runs for longer before the faster bit of road) and would you believe it? no stuttering at all, either time..
This is just weird. Same fuel, same bit of road, car running for the same length of time, and nothing wrong.
Could it be a dodgy plug or lead?