14.Subsection (1): section 12 of the Criminal Appeal Act 1968 makes provision for an appeal against the verdict of not guilty by reason of insanity.  Sections 13 and 14 of the 1968 Act (reproduced on pages 5 and 6 of these notes) set out the powers of the Court of Appeal on an appeal under section 12.  Subsection (2) applies those provisions to the reference of a verdict of guilty but insane with minor modifications.
15.In brief, section 13 deals with the disposal of an appeal under section 12, requiring the Court of Appeal to allow the appeal if they think that the verdict is unsafe, and to dismiss it in any other case.  Where the Court finds that the accused was not insane but was guilty of an offence, they can substitute a verdict of guilty of that offence, and shall have like powers of dealing with the appellant as the court at trial would have had, except that the death penalty cannot be imposed.
16.Section 14 of the 1968 Act provides that, if the Court of Appeal concludes that the proper findings in a case in which there has been an appeal under section 12 would have been that the accused “was under a disability and that he did the act or made the omission charged against him”, the Court of Appeal shall either make an order that the appellant shall be admitted to hospital, or, where they have the power to do so, a guardianship order, supervision and treatment order, or an order for the appellant’s absolute discharge.  Because there could not have been such findings in cases before the Criminal Procedure (Insanity and Unfitness to Plead Act) 1991, subsection 2(2)(b) has the effect of requiring the Court in these cases to consider not what findings there should have been, but simply what the facts of the case are.
Commentary on Sections Section 2: reference treated as an appeal: England and Wales