I went through this stage at 17-18, my first car was a citroen ax gts,put 17 " wheels on tinted the lights, stupid 4" exhaust, stood back and thought cool lol.
If you like it thats all that matters as its yours and your taste but just start to have a look around you will start to see what people are saying to you, less is more, big wheels just dont suit small cars especially halfords specials, clean lines with only subtle body mods, standard rear lights definately, smaller wheels from another model clio maybe, lowered but not ott or you will ruin the ride and the shocks.
You only need a different back box with a 2.5" tail to be in keeping with the rest of the car, anything more and you may find pics on barry boys.
Give the mudflaps to marti Mc fly, he will take them back to 1985 for you.
Sound system fair enough, but more weight = less speed, will also affect the handling and braking but your choice, at 17 i wouldnt be without my stereo man.
Just remember, next time your at the lights and you look over and the guy/girl looks like they are on the phone laughing and shaking their head, they are not on the phone mate, they are admiring your ride.
All is not lost however, just keep the hoodie on, right hand top centre of the wheel and lean left, job done.