Yes, the plastic tray in the boot acts as a mudguard to a point, keeping everything above it relatively clean and dry. But everything that is in front of the rear wheel, behind the seat backs, including the exposed seat belts on early models (like mine), gets absolutely filthy. Nothing like your wife getting all gussied up to go out in style, only to upon sitting in the Morgan pull the seat belt on and end up with a muddy-road-grimy smear on her shoulder.
Ahhhhh....another great reason not to have one of those (wives)!