Ok, thanks for those answers. I have been thinking about this and have a vague memory of a review of the Om4ti in which they were surprised by the supplied lens not being very sharp. I wonder if there was a bad lot? I can't see that there could be anything wrong with the camera that would spoil sharpness. The pressure plate looks ok. The lenses are so cheap that I may get another one to try. I wonder if I am being too fussy?

Rick and Jim- I will have a close look at the lens.
Dave