Richard,

You are correct that the guidance is not strictly an SI - since it has no SI number. It went through the exact procedure applicable to an SI subject to affirmative resolution and had a considerably longer debate in the Commons Standing Committee than most such SIs (but that was under two hours). The joint committee on statutory instruments also considered it and suggested two changes one of which was incorporated and the other was not prior to the two house committees considering it. The lords committee passed it without opposition. The