Looks great.
I've just given this a go but have run into a problem. While I can locate the Thickbox content by viewing source direct from the website, in Sitecore's HTML tab I simply have:
<tr>
<td style="WIDTH: 10px" colspan="2"><a class="thickbox" href="#TB_inline?go=go&height=390&width=300&inline Id=scopeMenuDealer"><img style="WIDTH: 330px; HEIGHT: 77px" border="0" src="~/media/MINI/Anneka%20Sanghera/Main%20Image%20%20%20MINI/Home%20%20%20Find%20a%20Dealer.ashx"></a></td></tr>
...It looks like I can't edit the content that is in the Thickbox within SiteCore.