I know what you are talking about and i think this noise comes from boat side. I bought original two face cargo tray and after fitting that, car became more silent than before. So can recommend you to buy a cargo tray and try with it so.
And if your tires are turanza T001 you may also think about to change themself Because They are really noisy tires.
As you know there are 4 kind of antenna is available for astra k Which you can see them in the attachment.
My car has the longest antenna of 4 of them [Blockierte Grafik: http://www.astrakforums.co.uk/images/smilies/icon_lol.gif]so i wanna change it with a shark finn. I want something like fourth car's antenna -large one-. But i need some recommendation.
Thank you!(:
