Hi,
From memory, there are three plastic clips (one at the front, one in the middle and one at the rear) that you need to unclip and it will then come off (obviously still attached by the wires for the electric seats though). You will need to reach under the seat to undo the middle clip. When I replaced my broken middle clip, I had to push quite hard on the whole assembly and reach under with my other arm to get it to clip into place.