I dont know how I missed this topic but fair play you got the result you were looking for in the end anyway!
Truth is always a good defence to an action for Defamation (Slander is the verbal whereas Liable is the written but they are both forms of Defamation).
Now that the economy is on its knees we have more and more clients seeking our advice as to whetrer they can legally do the same thing regarding their clients who have not paid them for goods or services for months. The thing to be aware of is the fact that if there is any area of dispute over the facts you could leave yourself open to a huge action for damages, so be very very careful before doing this.
Frawls