Cheers guys, I was able to set up a repeater inside the accordian no problem but I would like to take this a little further and have nested accordians.
For example in an Faq module.
The category Title is used in first accordian and repeater.
I would now like to have a second nested accordian and repeater showing the questions and answers only for the selected category.
I have sort of got it working to a point by binding the second repeater in the parent repeaters item data bound event but wondering how and where to catch the parent selection to bind the child repeater and accordian.

Repeater HTML code .
<div id="FAQCAT" >
         <asp:Repeater ID="rptCategory" runat="server"
             onitemdatabound="rptCategory_ItemDataBound">
            <ItemTemplate>
             <h3 class="SJFM_accordionHeader"><a href="#"><%# DataBinder.Eval(Container.DataItem, "FAQ_CAT")%></a></h3>
              <div class="SJFM_accordionContent">
               
                    <div id="FAQ" >
                        <asp:Repeater ID="Repeater1" runat="server">
                            <ItemTemplate>
                                <h3 class="SJFM_accordionHeader"><a href="#"><%# DataBinder.Eval(Container.DataItem, "Question")%></a></h3>
                                <div class="SJFM_accordionContent">
                                    <p>
                                        <%# DataBinder.Eval(Container.DataItem, "Answer")%>
                                    </p>
                                </div>
                            </ItemTemplate>
                        </asp:Repeater>
                      </div>
            </div>
        </ItemTemplate>
        </asp:Repeater>
        </div>
Code behind
protected void rptCategory_ItemDataBound(object sender, RepeaterItemEventArgs e)
        {
            if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                 Repeater FaqList = (Repeater)e.Item.FindControl("Repeater1");
                if (FaqList != null)
                {   // now want to pass the category id to this but how and from where
                    FaqList.DataSource = SJFM_SQL1.FAQ();
                    FaqList.DataBind();
                  
                }
            }

        }

That worked,  in case anyone else is interested this is how you cast the dataitem.

string cat =  (string)DataBinder.Eval(e.Item.DataItem, "FAQ_CAT");
int ID = (int)DataBinder.Eval(e.Item.DataItem, "FAQ_CATID"); 

Many thanks Stuart