The best thing for you to do is go into your local building department and ask an inspector about it (or review the local code yourself if you feel comfortable doing so). The code requirements on these things can vary greatly from place to place.

There should be no clearance to cumbustables for an Electric Unit. They typically only put out around 5,000 BTU's, so you should be fine. Basically the same thing as setting a Space Heater on your floor. If you're really concerned though, dig out your Manual on the FP. It will state the clearances in there. If you no longer have it, find the manufacturer and model and look it up online.