Yes, I agree, the aerodynamics conspire to suck muck up and deposit it on the tailgate and rear window.Thanks for the feedback. I should have identified my car as the Mk II 40kWhr version. I've had hatchbacks and SUVs before but none have got as dirty as this car does so soon; the aerodynamics must be poor as the car can literally get dirty within 10 miles on a wet day. Annoyingly, the rear bumper gets filthy which is a problem for keeping your clothes clean when loading and unloading the boot.
Pity as we quite like the car apart from that, good size, range and performance. Fittings and interior are a bit basic and low end quality materials but I suppose that is a reflected in the price. List of optional extras and upgrades is very limited, I would have liked an adjustable steering column and brighter headlamps at the very least. I also don't need heated rear seats.