Gordon’s Alive! The cat in this O2 TV ad has decided to ‘be more dog’ – running, chasing cars, sticks, grabbing frisbees and such. The main song is Flash by Queen, from the soundtrack of the 1980 movie Flash Gordon. You can download Flash from iTunes.
UPDATE: As noted by commenters including Humble77, the beautiful piano piece at the very beginning of the ad is Gymnopédie No.1, composed by French pianist Erik Satie. You can also download Gymnopédie No.1 from iTunes.