(3)     Where an action is brought either by the owner of the copyright or by the exclusive licensee, and the action, in so far as it is brought under section 37, relates (wholly or partly) to an infringement in respect of which they have concurrent rights of action under that section, the owner or licensee, as the case may be, shall not be entitled, except with the leave of court, to proceed with the action, in so far as it is brought under that section and relates to that infringement, unless the other party is either joined as a plaintiff in the action or added as a defendant; but this subsection shall not affect the granting of an interlocutory injunction on the application of either of them.

    (4)     In any action brought by the exclusive licensee by virtue of this section, any defense which would have been available to a defendant in the action, if this section had not been enacted and the action have been brought by the owner of the copyright, shall be available to that defendant as against the exclusive  licensee.

    (5)     Where an action is brought in the circumstances mentioned in subsection (3) and the owner of the copyright and the exclusive licensee are not plaintiffs in the action, the court, in assessing damages in respect of any infringement as it mentioned in that subsection -----

              (a)   if the plaintiff is the exclusive licensee, shall take into account any 
                      liabilities (in respect of royalties or otherwise) to which the license is 
                      subject; and

              (b)   whether the plaintiff is the owner of the copyright or the exclusive
                      licensee, shall take into account any pecuniary remedy awarded to the 
                      other party under section 37 in respect of that infringement, or, as 
                      the case may require, any right of action exercisable to the other party 
                      under that section in respect thereof.

        (6)   Where an action, in so far as it brought under section 37, relates (wholly or partly) to an infringement in respect of which the owner of the copyright and the exclusive licensee have concurrent rights of action under that section, and in that section (whether they are both parties to it or not) and account of profits is directed to be taken in respect of that infringement, then subject to any agreement of which the court is aware whereby the application of those profits between them as the court may consider just and shall give such directions as the court may consider appropriate for giving effect to the apportionment.