Welcome to the Werkz.
Have look at Felgen-Katalog - BMW-Treff - der Treffpunkt für alle BMW-Fans und -Fahrer
for the details of your current wheel, including the offset which I suspect will be the sticking point for the current wheels that you are looking at.
To see what affect the different parameters have on the tires position relative to the rest of the car have a look at Wheel-Tire size comparer - RIMSnTIRES.com
, it will let you fiddle around with all of the relevant figures before you go and buy something that doesn't suit your car.
Good luck and enjoy your time here.