This song was in a car advert about a month ago. It's also in this advert here. CLICK HERE (Might take a while to load because it is in a high quality quicktime format.)
It's called 'Hush.' I think Deep Purple did the original. But the version i remember is by Kula Shaker. Though the version used in that advert seems to be a live version. I'm guessing it's Kula Shaker.