Dont get big wheels, they ruin handling and performance.
Crap.
Dal's had 17" wheels on his for years which
improved the handling.
In the end, it's all down to you what you do with your car. There will always be people who like or dislike what you do aswell, the trick is to only do what you're happy with, and not because other people think you should.
Performance mods: air filter (negligable need), SS exhaust, ecu re-map, FRP air intake (££££), throttle bodies (£££££££££££££)
Handling: lowering kit, bigger wheels, suspension bushes.
Looks: wheels, bodykit - spoilers (sorry Rob), side skirts, fog lamps, headlights (Halford Extreme Brilliance are good , don't
need HIDs)
Interior: Door cards and seats, stereo, glove box light (more useful than you'd think!), a second light in the boot, interior LED bulbs.
You're only limited by your imagination and your budget. Or if you're doing it yourself, your ability.