Looked at regulations and they are badly written but my take is:
In the case of a motor cycle or a motor tricycle which does not have a body of a type which is characteristic of the body of a four-wheeled vehicle
will not cause the courts to have the same view as you. This says, 'characteristic' not compliant, and my take on the body style is a body that has twin front headlamps and parallel seating is 'car like'.
You may get away with not having one for a while, but I think the MOT inspector could well fail it for not having one.
