Depends how serious you want to be.
You need sport from wings or the bumper is too wide. You can sand/fill it, but that's a bit of a ball ache. Then there's grille/bumpers/skirts/arch liners/interior/xenons. Plus telling your insurance.
TBH, save your cash. If you want to mod it get a set of alloys and lower it a bit. Done. Otherwise you'll spend £2k on parts/paint then in a year realise it's still slow and you want something faster. Your car is now worth £500 more than a normal 1.2 because people just aren't bothered that it's a rep and the insurance increase etc. Unless you return it to standard. But even then, still a massively pointless exercise.