When I took my car to the dealership to investigate they said everything is normal. I showed them how my tires weared different to one of their own cars, and they still think its normal. I sent my query to Good Year and they said the same.
I asked BMW to check the alignment, they said it doesn't need doing but I insisted. In turns out that they did need adjusting. The road noise improved a little but I still wasn't happy as I know this is not normal. I didn't enjoy driving my car nor was I able to enjoy my music no matter how loud it was.
In the end I swapped my 20's with 19's, the difference was day and night. I also add extra door rubber trims (bought from ebay) and placed it where I can to ensure all doors are sealed properly which also improved eliminating some road noise particularly on rainy days.
I still think that the F10 has better road noise insulation though.
In your case given that you have 18's, I'd check wheel alignment and tyre condition.
Let us know how you get on.
Hope this helps.