This afternoon I spent an hour on the drive way swapping out sidelight and indicator bulbs on my 172.
Gone are the nasty weak yellowish side light bulbs, in place are Philips blue vision W5W bulbs which give out a crisp brilliant white light which matches the xenon units....the yellow sidelights are a flaw on clio 172/cups...but these £7.50 bulb sets give real bang for the buck. But the drivers side- side light bulb can be a bast#$D to take out and fit.
Secondly I changed the orange indicator bulbs which didnt look right on clear cluster headlamp units front and back...in place now are Philips PY21W Silver vision bulbs....they look trick but finish the car off nicely.
If you were to do one thing with the bulbs on your car, I would recommend the W5W philips blue vision bulb change over above anything else.
Next month I am going to fit Philips Premium plus main beam bulbs which give 50% more bright light.