Coconut matting has always been the traditional flooring option for marquees.  It is 12mm thick, reuseable material that runs in widths along the marquee over a plastic ground sheet.  It is still very popular because of its specific style and reasonable cost to hire.

It can be a more suitable option if you do not wish to go to the expense of hiring a wooden boarded floor.  The reason being is that corded carpet is very thin in comparison and will show every lump and bump.  Where as a relatively thick matting is less likely to show the natural contour of the lawn.