Theft? stealing? Surely the IPO knows that it's called infringement!
There is no such thing as stealing someone's song in UK copyright law. The copyright can be infringed by copying the song, the song is not stolen.
The Theft Act (1968) defines 'theft' as: "A person is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it"