I don't think Parliament intended for police to get a warrant when they passed this legislation. I think they put in the first clause “if you have a warrant”...in other words, if you have lawful authority. I don't think Parliament intended for that to mean a warrant. I think it was left sort of ambiguous, so it has been interpreted by some to suggest you need a warrant.
Again, as my friend suggested, you're really looking at someone's name and address, perhaps. You can get that off their licence plate. You can stop someone on the street and ask them to identify themselves. You don't need warrants for those things. So I think the protections are built in to the process now.