What you are referring to is the false floor, which was standard for the SE spec vehicle, but not the Sport, which explains the difference. It can be added on at moderate cost (£200-ish) with a bit of time and effort.
The SE also got fogs, illuminated vanity mirrors and other minor 'comfort & convenience' related items, whereas the Sport got sport seats, 17" wheels and sport suspension, full DIS (the readout between the dials) and a 3 spoke steering wheel.
Cheers,
Mike