Hi Phil
not to worry, I found the solution. For some reasons (????) the template designers have decided not to allow the user to select a specific main menu. Fagus has the menu ‘mainmenu’ hardcoded into the php sources. So if you decide to name your main menu differently you wont get any menu!!!.
The trick is to copy the template as you suggested, rename it and make some changes (so called hacks) to the php files to point to the menu you would like (e.g. altmainmenu). Then you can link specific pages to the new template and you will also get them shown with your selected main menu.
Just get back to me if you need more infos on this.
Cheers
Stephane