I wouldn't bother with aftermarket body kits - they are pretty horrible.
You should be able to get oem sideskirts, rear wing and tailpipes to make it sportier (the sporting models have these features).
One of the first mods to do (imo) is to replace the standard bulbs. Osram nightbreakers or similar for the main H4 bulbs (halfords do great +90% on bogof from time to time), philips bluevision sidelights and Osram Diadem Blue indicator bulbs. You may also want to replace the number plate bulbs with philips blue vision (same size as sidelights). These are subtle mods but make a positive difference to the appearance and make things better at night by improving the distance vision.