Can anyone tell me what are the correct sidelights for 2004 facelifted Cooper S, as I want to upgrade to some brighter ones as the ones fitted are yellow and dim.
Also what are the best ones to go for at a decent price?

I use OSRAM Cool Blues (W5W) on my R56. Maybe ask your local dealer what the bulb code is, but I'm sure someone here can help.

The Cool Blues match my fog lights perfectly, so when they are both on, it looks like one unit. I also used them in my MK7 Fiesta with OSRAM Nightbreakers and I got the same uniform look. You can also try Philips Silvervision and I've seen PIAA bulbs also on the internet, but I've had not experience with the PIAA brand.