The Xfce main menu is quite basic & without directly editing the code, quite hard to change. While researching this, I came across references to the Whisker menu. Did a little researching, turns out is is not in the Wheezy repo’s. It is available in Debian testing, but required multiple dependences (new versions in some cases.) So, not an option.
A little more searching led me to this openSUSE (weird I know) website witch gives a Debian link. When followed it offers a new repository for you to add, where the package is held. There is also the option of downloading a binary file, either xfce4-whiskermenu-plugin_1.5.0-1_i386.deb or xfce4-whiskermenu-plugin_1.5.0-1_amd64.deb. Downloaded i386 for my machine, then installed via Gdebi package installer. Then I right-clicked on the Panel> Panel> Add New Items…> Whisker Menu. Works a treat!