Yes, the 18's look great on our cars!
The BMW dealers recommended sizes are 225/40/18 front and 255/35/18 rear. After my first puncture on the rear and subsequent costly replacement, I changed the back to 245/40/18 and it still looks great, but cost R500 less per tyre!! I've got the Bridgestone Potenza's but there are some other great tyres out there. For example the Michelin Pilot Sport II or the Pirelli Zero's