Ok, not implemented yet, thanks for clearing that up.
Brett

A quick summary of the solution:

The scrollable data table has a binding attribute 'sortOrder' which binds to a bean property of type SortOrder.

 <rich:scrollableDataTable id="${id}notesTable" var="note"
 value="${noteActionEntity.notes}"
 selection="${noteActionEntity.noteSelection}"
 binding="${noteActionEntity.noteDataTable}"
 sortMode="single" selectionMode="single" sortOrder="${noteActionEntity.order}" height="172px" width="570px">


 <rich:column width="170px" styleClass="centre" sortExpression="noteSourceParty.formalPartyName">
 <f:facet name="header">
 <h:outputText value="#{messages.noteLodgedByLabel}" />
 </f:facet>
 <t:outputText value="${note.noteSourceParty.formalPartyName}" />
 </rich:column>
 <rich:column width="140px" styleClass="centre" sortExpression="messageDate" >
 <f:facet name="header">
 <h:outputText value="#{messages.noteDateLodgedLabel}" />
 </f:facet>
 <h:outputText value="${note.messageDate}" />
 </rich:column>
 <rich:column width="136px" sortExpression="messageText">
 <f:facet name="header">
 <h:outputText value="#{messages.notePreviewLabel}" />
 </f:facet>
 <t:outputText value="${note.messageText}" />
 </rich:column>

 <rich:column width="100px" sortExpression="messageAck">
 <f:facet name="header">
 <h:outputText value="#{messages.acknowledgedLabel}" />
 </f:facet>
 <t:outputText value="${note.messageAck}" />
 </rich:column>


 </rich:scrollableDataTable>

 /**
 * A binding attribute on the note data table used to control the initial sort order.
 */
 private SortOrder order = new SortOrder();




 public AbstractNoteControllerBean() {
 // Initially sort on the messageDate column false indicates DESCENDING.
 // messagedate corresponds to a property on the Datatype that is being
 // iterated on in the table
 SortField[] fields = {new SortField("messageDate", false)};
 order.setFields(fields);



 }

 /**
 * @return the order
 */
 public SortOrder getOrder() {
 return order;
 }

 /**
 * @param order the order to set
 */
 public void setOrder(SortOrder order) {
 this.order = order;
 }