I found the answer on www.whatsthatcalled.com and it is a song from the soundtrack of 28 days called
"In The House - In A Heartbeat" by John Murphy
Fantastic song, isn't it ?
I dont think that is the correct answer! If I have the right ad in mind then the track is by 'Godspeed You Black Emperor' and is called 'East hastings'. It is from the Film 28 Days Later but NOT on the soundtrack.