Perch Mega Menu

Hi

I'm trying to add Perch nav to my Mega Menu (yamm/bootstrap). This is where I'm currently at;

level 1

<perch:before> 
    <div class="navbar yamm navbar-default navbar-bar">
        <div class="container">
            <div class="navbar-header">
                <button type="button" data-toggle="collapse" data-target="#navbar-collapse-1" class="navbar-toggle">
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </button>
            </div>
            <div id="navbar-collapse-1" class="navbar-collapse collapse">
                <ul class="nav navbar-nav">
                    </perch:before>
                    <li class="<perch:if exists="current_page">active </perch:if><perch:if exists="ancestor_page">ancestor </perch:if><perch:if exists="subitems">dropdown yamm-fw </perch:if>"> <a href="<perch:pages id="pagePath" />" <perch:if exists="subitems"> class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false"</perch:if>><perch:pages id="pageNavText" /></a>  <perch:pages id="subitems" encode="false" /> </li><perch:after>
                </ul>
            </div>
        </div>
    </div>
</perch:after>

Level 2

<perch:before> 
    <ul class="dropdown-menu">
        <li>
            <div class="yamm-content">
                <div class="row">
                    <div class="col-sm-3 yamm-nodivider">
                        <ul>
                            </perch:before>
                            <li>
                                <a  class="btn btn-primary yamm-btn" href="<perch:pages id="pagePath" />"><perch:pages id="pageNavText" /></a>
                            </li>
                            <perch:after>
                        </ul>
                    </div>
                </div>
            </div>
        </li>
    </ul>
</perch:after>

My original nav (part of it)

<div id="navbar-collapse-1" class="navbar-collapse collapse">
            <ul class="nav navbar-nav">
                <li><a href="/">home</a></li>
                <li class="dropdown yamm-fw">
                    <a href="/surgical" class="dropdown-toggle" data-hover="dropdown" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">surgical <span class="caret"></span></a>
                    <ul class="dropdown-menu">
                        <li>
                           <div class="yamm-content">
                                <div class="row">
                                    <div class="col-sm-3 yamm-nodivider">
                                        <ul>
                                            <li><a class="btn btn-primary yamm-btn" href="/surgical/facial">facial treatments</a></li>
                                            <li><a class="btn btn-primary yamm-btn" href="/surgical/breasts">breast treatments</a></li>
                                            <li><a class="btn btn-primary yamm-btn" href="/surgical/body">body treatments</a></li>
                                        </ul>
                                    </div>
                                    <div class="col-sm-3">
                                        <span class="submenu-headers">Facial treatments</span>
                                        <ul>
                                            <li><a href="/surgical/facial/blepharoplasty">blepharoplasty</a></li>
                                            <li><a href="/surgical/facial/dimple-surgery">dimple surgery</a></li>
                                            <li><a href="/surgical/facial/otoplasty">otoplasty</a></li>
                                            <li><a href="/surgical/facial/facelifts">facelifts</a></li>
                                            <li><a href="/surgical/facial/necklifts">necklifts</a></li>
                                            <li><a href="/surgical/facial/rhinoplasty">rhinoplasty</a></li>
                                        </ul>
                                    </div>
                                    <div class="col-sm-3">
                                        <span class="submenu-headers">Breast treatments</span>
                                        <ul>
                                            <li><a href="/surgical/breasts/enlargement">enlargement</a></li>
                                            <li><a href="/surgical/breasts/reduction">reduction</a></li>
                                            <li><a href="/surgical/breasts/uplift">uplift</a></li>
                                        </ul>
                                    </div>
                                    <div class="col-sm-3">
                                        <span class="submenu-headers">Body treatments</span>
                                        <ul>
                                            <li><a href="/surgical/body/bodytite">bodytite</a></li>
                                            <li><a href="/surgical/body/cellulite">cellulite</a></li>
                                            <li><a href="/surgical/body/liposuction">liposuction</a></li>
                                            <li><a href="/surgical/body/mini-tummy-tuck">mini tummy tuck</a></li>
                                            <li><a href="/surgical/body/smart-lipo">smart lipo</a></li>
                                            <li><a href="/surgical/body/vaser-lipo">vaser lipo</a></li>
                                            <li><a href="/surgical/body/weight-loss-surgery">weight loss surgery</a></li>
                                        </ul>
                                    </div>
                                </div>
                            </div>
                        </li>
                    </ul>
                </li>
                           Next dropdown
                           etc., etc.

My current templates gets me to first col-sm-3 in the dropdown, but I've hit a wall on how I produce the next subitems in the next two columns.

Has anyone got any suggestions/pointers?

Thanks Wayne