A counterclaim is very similar to the original particulars of claim, but this time it would be your spouse setting out and asking the court what he or she wants the court to order. If your spouse wants to enter a counterclaim, he or she has to do serve it on you at the same time as his or her plea.
The basic content and style of the counterclaim will be almost exactly like that of the original particulars of claim.
It would be useful for you to make a photocopy of the counterclaim and make some notes at each paragraph, indicating whether the contents are true or not, and where appropriate giving a short explanation. This will then help your attorney to help you to draft your plea to the counterclaim.