I thought there are only about 1.3-1.4 million Streamyx users. The other ISPs added to this would not make up 5 million. Or is the 5 million the number of people using broadband, ie maybe many users sharing an account at home etc.

6.1% of approx 28 million comes to approx 1.7 million, which sound right. 5 million users out of 28 million population is approx 17% which I doubt we have achieved.